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Speaker 4: When we set out to understand the universe, we usually

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Speaker 4: start by looking up. After all, that's where the best

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Speaker 4: views are of the glittery cosmos stretched across billions of miles.

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Speaker 4: We wonder, are we alone? Is there anyone up there

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Speaker 4: looking back at us? But what if the best way

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Speaker 4: to find answers to questions about what's up there? Is

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Speaker 4: actually to look down under our feet. Hi, I'm Daniel.

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Speaker 4: I'm a particle physicist and a professor at UC Irvine,

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Speaker 4: and I desperately want to know who's out there in

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Speaker 4: the universe and if they are wondering the same things

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Speaker 4: we are. And Welcome to the podcast Daniel and Jorge

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Speaker 4: Explain the Universe, in which we do just that, wonder

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Speaker 4: about the nature of the universe and try to explain

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Speaker 4: all of it to you. Regular listeners the podcast know

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Speaker 4: that I am desperate to understand the nature of the universe,

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Speaker 4: how it all works, and to explain all of that

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Speaker 4: knowledge and all of that confusion to you. One of

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Speaker 4: the deepest questions we wrestle with on the pod is

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Speaker 4: not just about the universe, but kind of about ourselves.

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Speaker 4: How weird? Are we? Are there more like us out

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Speaker 4: there in the universe? Or are we alone? How rare

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Speaker 4: and special is the Earth anyway? Are we one of

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Speaker 4: a kind out of a trillion planets? Or are we

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Speaker 4: one of many rocky balls covered in Curious Life. We're

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Speaker 4: frustratingly limited by what we can learn about distant planets,

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Speaker 4: though we're doing our best. But something we can do

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Speaker 4: right now is drill deeper into our own planet, understand

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Speaker 4: the forces that shaped it, and whether those are finely

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Speaker 4: balanced in a rare way or naturally in harmony, in

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Speaker 4: a way we'll find everywhere in the universe. So today

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Speaker 4: on the podcast, we'll be answering the question what's hidden

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Speaker 4: inside planets? And to help me explore this fascinating topic,

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Speaker 4: I'm pleasing to be speaking to Professor Sabina Stanley, author

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Speaker 4: of a very recent book of that same title. All right, well,

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Speaker 4: then it's my great pleasure to introduce the podcast Professor

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Speaker 4: Sabina Stanley. She's the Bloomberg Distinguished Professor of Planetary Physics

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Speaker 4: at Johns Hopkins University, where she focuses on magnetic fields

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Speaker 4: and other geophysical elements as a means of studying the

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Speaker 4: interiors of planets, moons, and asteroids. She's an Alfred Peaceloan

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Speaker 4: Research Fellow and has also received the William Gilbert Award

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Speaker 4: of the American Geophysical Union. Sabina, Welcome to the podcast,

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Speaker 4: and thank you for coming to talk to us.

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Speaker 6: Thanks so much for having me.

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Speaker 4: So. One thing we always wonder about as we look

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Speaker 4: out into the night sky is all the other planets

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Speaker 4: that are out there. Of course, we can't study many

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Speaker 4: of them up close, and so often on this podcast

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Speaker 4: we've tried to dig into what's under our feet, the

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Speaker 4: mysteries that are right here in our Earth. And so

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Speaker 4: I really enjoyed your recent book, What's Hidden Inside Planets,

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Speaker 4: and I'd love to talk to you about what's in

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Speaker 4: our planet. Could you start us off by taking us

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Speaker 4: sort of on a brief tour of like what is

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Speaker 4: under our feet, layer by layer, all the way down

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Speaker 4: to the core.

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Speaker 6: Yeah, absolutely, great question.

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Speaker 7: So I think it's interesting to note that when you

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Speaker 7: start on the surface, as you go deeper and deeper,

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Speaker 7: stuff gets kind of weirder and weirder and much more

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Speaker 7: different than what we're.

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Speaker 6: Used to on the surface. So we start on the crust.

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Speaker 7: This is where we live, This is where all the

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Speaker 7: stuff happens that we're used to. Crust can vary in

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Speaker 7: thickness five about you know, five kilometers depth to almost

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Speaker 7: one hundred klmeters depth. But under that you get to

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Speaker 7: the mantle that's also still mostly rocky, the type of

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Speaker 7: rocks that are rich in magnesium and silicates, but still

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Speaker 7: what we would recognize as rocks. So about half the

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Speaker 7: radius of the earth are those rocks. It goes down

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Speaker 7: about two thousand miles deep.

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Speaker 4: So what distinguishes then between the crust and the mantle.

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Speaker 4: Is it like how squeezed they are and how much

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Speaker 4: they flow? Is it a different kind.

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Speaker 6: Of rock, great question.

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Speaker 7: Yeah, it's a little bit different kind of rock. So

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Speaker 7: essentially the crust layer of the earth. I sometimes referred

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Speaker 7: to it as like the scum of the earth. So

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Speaker 7: it's kind of like, you know, like when you're making

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Speaker 7: a soup and you're boiling your broth and you've got

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Speaker 7: all that light, floaty stuff that comes to the top.

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Speaker 7: So the stuff that's the most buoyant when you have

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Speaker 7: certain heat, thermal reactions and chemical reactions happening with rocks

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Speaker 7: near the surface, all of that percolates up to the

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Speaker 7: top and that ends up becoming the crust, and then

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Speaker 7: sort of the stuff underneath might be less scummy, less

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Speaker 7: you know, it's been less reworked, and it's sort of

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Speaker 7: more kind of pristine rock.

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Speaker 4: I see, we're going to get started very quickly with

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Speaker 4: the food analogies.

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Speaker 6: Yeah, I'm sorry, it's just going to be how it goes.

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Speaker 7: It's going to be food involved in almost every analogy

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Speaker 7: I make here.

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Speaker 4: Are you a big fan of soup or you a

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Speaker 4: cook at home?

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Speaker 7: So I'm a terrible cook, but I grew up in

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Speaker 7: a restaurant family, so I've been around sort of good

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Speaker 7: food my whole life.

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Speaker 4: All right, Well, then let's do our best to at

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Speaker 4: least use tasty food analogies. I don't want anyone to

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Speaker 4: think that the earth is like a disgusting bowl of soup.

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Speaker 4: Maybe it's like, you know, bubbling hot cocoa, and this

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Speaker 4: is that delicious film that forms on top.

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Speaker 6: I love that so much you don't even know.

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Speaker 4: So that's amazing, all right. So the crust is the

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Speaker 4: sort of coolest part that floats to the top, and

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Speaker 4: underneath that it's still rock, but it's able to flow.

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Speaker 4: How do we visualize that? I mean, it's not like

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Speaker 4: liquid lava that's flowing on the surface. This is still

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Speaker 4: like solid rock, but it's flowing. How does solid rock flow?

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Speaker 4: Is something I've always tried to visualize and failed.

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Speaker 6: Yeah, so the answer to that question is very slowly.

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Speaker 1: Right.

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Speaker 7: So, yes, it's solid, but it's still deformable, right, And

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Speaker 7: I think we have experience with different types of solids

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Speaker 7: in our everyday life, and that some are more deformable

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Speaker 7: than other.

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Speaker 6: Right, Like you might have clay.

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Speaker 7: Clay is solid, but you can still deform it, whereas

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Speaker 7: a metal also is kind of deformable. But then you

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Speaker 7: have some rocks that are really like a diamond, really

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Speaker 7: hard to deform.

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Speaker 6: But the rocks in the.

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Speaker 7: Mantle, they are solid, but they can be deformed. And

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Speaker 7: if they can be deformed, then they start being influenced

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Speaker 7: by the forces like gravity such that you can get

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Speaker 7: them to flow.

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Speaker 4: I see, all right, So we have the crust and

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Speaker 4: we have the mantle, both of which are still really rock.

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Speaker 4: Take us down below.

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Speaker 7: That, right, So then you get down about halfway through

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Speaker 7: the Earth, and you only hit a very big boundary,

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Speaker 7: complete change of environment. Now you're at the iron core.

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Speaker 7: So the inner half of the planet about it's mostly

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Speaker 7: made of iron. There's a little bit of nickel mixed

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Speaker 7: in there, and about ten percent of some sort of

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Speaker 7: lighter elements that we have a whole sort of platter

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Speaker 7: of possibilities for but we don't actually know what they are.

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Speaker 7: And that makes up the core. The core has two

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Speaker 7: parts to it. The outer port is liquid. It can

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Speaker 7: flow very easily, much faster timescales than the mantle, and

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Speaker 7: it's really important for us because that's where our magnetic

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Speaker 7: field is generated in that liquid iron core. Then below that,

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Speaker 7: the innermost thirteen hundred kilometers of our planet is a

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Speaker 7: solid iron core.

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Speaker 4: And so what distinguishes then the mantle, which can flow

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Speaker 4: but is a solid not a liquid, from the outer core,

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Speaker 4: which can flow but is a liquid and not a solid, Like,

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Speaker 4: is there really a distinction here? Are we just putting

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Speaker 4: labels on things?

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Speaker 7: When we study fluid dynamics, we talk a lot about

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Speaker 7: there being a spectrum of fluids. Right, nothing's ever purely

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Speaker 7: a solid that are purely a fluid. It's all about

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Speaker 7: the time scales. So the mantle, for example, if you

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Speaker 7: want to talk about how materials flow in the mantle,

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Speaker 7: a parcel at the bottom of the mantle could take

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Speaker 7: hundreds of millions of years to make it to the

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Speaker 7: top of the mantle, whereas a parcel at the bottom

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Speaker 7: of the core could take a couple of years to

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Speaker 7: get the top of the core. So it's a very

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Speaker 7: different timescale of the flow. You could actually see changes

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Speaker 7: in material in the core flowing, but.

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Speaker 4: There's also like a boundary. It's not like there's a smooth,

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Speaker 4: very gradual transition. There's like a line. You can say,

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Speaker 4: this is the core and this is the mantle.

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Speaker 7: Yeah, and that happens because mantle, rocks, and iron in

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Speaker 7: the core have very different densities, and at one time

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Speaker 7: in the past in our planet, it was mostly molten

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Speaker 7: and so the heaviest stuff, when you have a bunch

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Speaker 7: of stuff mixed together, the heaviest stuff's going to sink

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Speaker 7: to the bottom. And so that's what happened in Earth.

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Speaker 7: All the iron, most of the iron sunk to the

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Speaker 7: center of the Earth and made up.

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Speaker 4: The core like the big chunks in a stew or

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Speaker 4: something exactly.

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Speaker 6: Yes, I like it.

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Speaker 4: So the reason that there's a boundary there and like

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Speaker 4: a transition, and rather than just like a smooth gradation

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Speaker 4: from more liquid to less liquid, that reflects like the

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Speaker 4: phase transitions and materials. Is that right, the way that

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Speaker 4: like ice turns solid at some moment and doesn't just

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Speaker 4: like gradually become more and more solid.

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Speaker 7: I would say that's more representative of what kind of

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Speaker 7: happens at the inner core outer core boundary, so where

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Speaker 7: the iron becomes solid, but above that it's more kind

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Speaker 7: of like a maybe you go with an oil and

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Speaker 7: water type thing. You've got two materials with very different

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Speaker 7: density and very different properties, so it's really hard to

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Speaker 7: mix them.

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Speaker 4: Wonderful and tell us about how we know about this.

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Speaker 4: I was reading in your book this really exciting description

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Speaker 4: of the mantle race, basically like a parallel to the

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Speaker 4: space race, but into the Earth. Tell us about our

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Speaker 4: humanity's efforts to like literally tunnel to the center of

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Speaker 4: the Earth.

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Speaker 7: Yeah, So if you imagine you want to figure out

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Speaker 7: what's inside the Earth, right, your first instinct might be, hey,

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Speaker 7: why don't we dig down as far as we can

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Speaker 7: and actually sample it?

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Speaker 2: Right?

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Speaker 7: And it's a great instinct. Unfortunately, it's incredibly challenging to do.

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Speaker 7: And that's because pressure increases so fast as you go

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Speaker 7: deeper inside the planet, and so do temperatures.

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Speaker 6: So as you can imagine, humans.

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Speaker 7: Don't like really high pressures and temperatures, neither does equipment.

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Speaker 7: And the farthest we've been able to dig with sort

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Speaker 7: of a really concerted effort to do so, right, Like

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Speaker 7: this was something on the scale of moonshot to the

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Speaker 7: Moon in the late sixties. This is something very similar

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Speaker 7: to that, and you could get only down to about

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Speaker 7: eight miles in depth and the radius of the Earth

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Speaker 7: you're talking about four thousand miles, so tiny, tiny scrape

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Speaker 7: of the surface by going down that deep. Equipment does

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Speaker 7: not like high pressures and temperatures.

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Speaker 4: But how do you even get eight miles deep? I mean,

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Speaker 4: I remember digging in my backyard with a shovel, wondering

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Speaker 4: how far I could get, and it's not very far.

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Speaker 4: How do you get eight miles down?

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Speaker 7: This is like high tech technology kind of stuff. It's

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Speaker 7: at the limits of what we can do for drilling

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Speaker 7: that we do now to drill for resources, etc. So

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Speaker 7: it's a lot of fancy equipment and challenges that are

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Speaker 7: over met that way.

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Speaker 6: So we can't dig and we can't drill.

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Speaker 7: But that's okay because there are other ways we can

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Speaker 7: figure out what's going on deeper inside the earth.

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Speaker 4: Yeah, so tell us about some of those ways. You

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Speaker 4: were talking in the book about diamonds, how we can

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Speaker 4: use diamonds to give us little snapshots of what's inside

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Speaker 4: the planet.

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Speaker 6: Yeah.

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Speaker 7: So, you know, it would be great if we could

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Speaker 7: dig down, but when it'd also be great if the

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Speaker 7: stuff down there came to us. And that's really what

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Speaker 7: happens with diamonds. Diamonds are produced deeper inside the Earth

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Speaker 7: and then they come up to the surface, usually in

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Speaker 7: volcanic vent things known as kimber like pipes and those diamonds.

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Speaker 7: You know, Jewelers love diamonds when they're as pure as possible.

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Speaker 7: Geologists love diamonds when they're as impure as possible. So

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Speaker 7: sometimes diamonds, when they form, they can enclose a little

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Speaker 7: capsule of some of the material where they formed inside them, right,

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Speaker 7: So you might get a little bit of garnet in

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Speaker 7: the diamond, or a little bit of something that was

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Speaker 7: created deeper in the earth, and when it brings it up,

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Speaker 7: because diamonds so strong, it actually keeps the material in

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Speaker 7: its like pristine form. So you really have this like

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Speaker 7: sample from the interior of the Earth come to the surface

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Speaker 7: for us to investigate. So that's a great way, and

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Speaker 7: we've used that, for example, to figure out that there

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Speaker 7: is actually water deeper inside the Earth because we've found

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Speaker 7: water inside diamond inclusions.

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Speaker 4: It's fascinating to me though, that this thing that you

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Speaker 4: make in a higher pressure environment, when you bring it

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Speaker 4: up to low pressure, it doesn't explode. Is that just

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Speaker 4: because of the incredible structure of diamond.

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Speaker 7: Yeah, when they say diamonds are forever, that's technically not true, right,

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Speaker 7: They just have a really really long lifetime before they

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Speaker 7: revert back to their carbon phase. So yeah, it's just

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Speaker 7: a great property of diamond.

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Speaker 4: So is it's sort of like you know, you put

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Speaker 4: a pan of brownies in the oven and it changes

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Speaker 4: into something else, and when you take it out, cool

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Speaker 4: it down, it doesn't revert back into batter.

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Speaker 6: That's an excellent way of thinking about it.

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Speaker 4: Yeah, okay, and so then what have we learned from

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Speaker 4: these diamond samples, Like what's inside these diamonds that we

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Speaker 4: didn't realize other than water?

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Speaker 6: Yeah, I think water is the big thing.

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Speaker 7: Sometimes it's a lot about sort of the smaller amounts

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Speaker 7: of elements that we don't know about, right, how much

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Speaker 7: of a particular kind of silicon down there is sulfur

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Speaker 7: down there, these kinds of questions, and those all just

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Speaker 7: help us understand and what the building blocks of Earth

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Speaker 7: were they when Earth formed, and what the geochemistry the

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Speaker 7: kind of chemical reactions that can occur as material descends

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Speaker 7: into the Earth. That's really where we get that information.

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Speaker 7: But even with diamonds, right, we're talking about the outermost

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Speaker 7: layers of the mantle, right, diamonds. We don't get diamonds,

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Speaker 7: say from the core mantle boundary or anywhere deeper than that.

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Speaker 7: So we can't use the diamonds to learn about the

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Speaker 7: deeper parts.

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Speaker 4: Is that because diamonds aren't made deeper or because diamonds

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Speaker 4: from that far down just don't make it up to

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Speaker 4: the surface.

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Speaker 6: Mostly the latter.

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Speaker 7: I think also, like if you get carbon down there, yeah,

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Speaker 7: it doesn't necessarily join into making diamond at that depth.

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Speaker 4: All right, So there aren't like huge diamonds buried deep

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Speaker 4: in the Earth that we are.

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Speaker 6: Not on Earth. Not on Earth.

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Speaker 4: Well, that was my whole motivation for digging so deeply

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Speaker 4: when I was a kid, fantasizing about revealing some you know,

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Speaker 4: boulder sized diamond. All right. So diamonds give us one

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Speaker 4: sample of what else can we do? What about gravity?

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Speaker 4: What about just studying like the variation in Earth's gravity

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Speaker 4: as we you know, orbit to play or look around it.

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Speaker 4: What does that tell us about what's inside the Earth?

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Speaker 7: The way I like to think about it is, you know,

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Speaker 7: if you want to figure out what's going on inside

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Speaker 7: the Earth, try and make an analogy to a human body. Right,

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Speaker 7: if you have an ache and you go to your

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Speaker 7: doctor and you're like, this hurts, Hopefully they're not. Their

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Speaker 7: first kind of instinct is not to drill a hole

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Speaker 7: in you to figure that out, Right, There are ways

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Speaker 7: that they can use different fields and different scans to

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Speaker 7: figure out what's wrong with your insides.

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Speaker 6: And we can do the same thing for the inside

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Speaker 6: of the Earth.

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Speaker 7: So we can scan gravity, as you mentioned, that's one,

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Speaker 7: magnetic fields is another one, and we can also determine

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Speaker 7: properties of waves that travel through the Earth from earthquakes

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Speaker 7: through seismology, So we can use all these scanning techniques

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Speaker 7: to figure out what's going on deeper inside the Earth.

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Speaker 4: So what do you mean by using gravity? Is it

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Speaker 4: just like measuring the variations of gravity so that we

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Speaker 4: understand how the Earth is not a perfect sphere or

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Speaker 4: how the Earth is not homogeneous in density? What is

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Speaker 4: it we're learning?

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Speaker 7: Yeah, great question. So, yeah, it really is the fact

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Speaker 7: that both isn't a perfect sphere and has some inhomogeneous

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Speaker 7: material below it. Right, So if you were walking around

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Speaker 7: with a grivi emitter that could measure gravity and it

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Speaker 7: was really really good, and you walked around, you would

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Speaker 7: get slightly different values everywhere you walk, and that would

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Speaker 7: be determined by the mass directly under your feet, and

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Speaker 7: so we can use that information. We have spacecraft that

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Speaker 7: are but the Earth that measure Earth's gravity feel to

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Speaker 7: really high precision, and we can use that to figure

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Speaker 7: out what is the distribution of density inside the Earth.

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Speaker 7: And that kind of allows us to kind of image

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Speaker 7: what's going on. Where's the denser stuff in the Earth,

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Speaker 7: where's the lighter stuff, And we can actually see things

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Speaker 7: like convection cells in the mantle and plumes of magma

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Speaker 7: coming up for volcanoes, things like this.

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Speaker 4: But gravity is such a weak force. How do you

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Speaker 4: identify these variations in density with such an incredibly weak force.

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Speaker 4: They must be pretty big effects.

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Speaker 6: They aren't.

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Speaker 7: They are very very tiny effect. We're just really good

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Speaker 7: at measuring them.

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Speaker 4: So a gravi emitter, you mentioned this might seem like

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Speaker 4: a weird object or listeners, but I guess like my

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Speaker 4: bathroom scale is a gravi emitter. If I walked around

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Speaker 4: the Earth with my bathroom scale, I would measure different

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Speaker 4: weights before and after lunch, of course, but also if

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Speaker 4: I didn't need anything, or are you use their reference mass,

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Speaker 4: then I guess that would measure different accelerations due to gravity.

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Speaker 6: Yeah.

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Speaker 7: Absolutely, And if you were someone on the surface taking

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Speaker 7: gravity measurements, that's exactly the kind of instrument you would use. Interestingly,

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Speaker 7: once we get into orbiting around a planet like Earth

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Speaker 7: to take measurements, we use a completely different technique. We

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Speaker 7: basically use the fact that if we have a spacecraft

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Speaker 7: in orbit around the Earth, we know it's in orbit

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Speaker 7: around the Earth, and its orbital speed and altitude is

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Speaker 7: completely determined by the mass of the planet.

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Speaker 6: So we can use things.

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Speaker 7: Like two spacecraft just slightly at different locations from each other,

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Speaker 7: kind of moving around, and we can use the distance

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Speaker 7: between the two spacecraft as like a proxy for how

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Speaker 7: much g is right where they are, how much the

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Speaker 7: gravity is right where they are. So that's actually how

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Speaker 7: it's done in practice with spacecraft.

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Speaker 4: Wow, that's incredible. And how sensitive are they? I mean

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Speaker 4: like one part in one thousand, one part in a million, Yeah.

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Speaker 6: One part in a million. That's where we're getting to.

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Speaker 4: Wow, So they can really tell if I've eaten lunch.

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Speaker 4: Some spacecraft up there can tell that the mass of

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Speaker 4: the Earth has changed.

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Speaker 7: One thing they're actually used for. So the great satellite

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Speaker 7: which orbited Earth for about ten years. One of their

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Speaker 7: main applications was to follow water flow on the surface,

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Speaker 7: so you could see, for example, when water was filling

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Speaker 7: reservoirs underground reservoirs in certain parts of the country or

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Speaker 7: different countries, if you wanted to see are we going

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Speaker 7: to have a drought, are we in a rainstorm season,

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Speaker 7: or what's the water situation going on here?

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Speaker 6: So we can even use gravity to tract climate change.

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Speaker 4: Wow, that sounds like modern day divining rods. But you're

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Speaker 4: actually using science to find the water underground. That's incredible,

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Speaker 4: all right, So gravity's one way to do it. You

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Speaker 4: also mentioned seismic probes. These are like waves inside the earth.

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Speaker 4: How do we use that to see what's going on?

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Speaker 7: So every time there's an earthquake, it's like sort of

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Speaker 7: something kind of punched the inside of the Earth at

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Speaker 7: some point and it causes the Earth to ring. It

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Speaker 7: causes waves to travel through the interior of the Earth

440
00:19:46,840 --> 00:19:49,080
Speaker 7: and on the surface of the Earth. If we put

441
00:19:49,119 --> 00:19:51,080
Speaker 7: out a bunch of instruments that can kind of measure

442
00:19:51,080 --> 00:19:54,840
Speaker 7: the shaking, so seismographs, then we can figure out a

443
00:19:54,840 --> 00:19:57,400
Speaker 7: few things about the earthquake waves we can figure out

444
00:19:57,440 --> 00:20:00,479
Speaker 7: when they arrive at different locations around the planet, and

445
00:20:00,520 --> 00:20:01,560
Speaker 7: how big the waves are.

446
00:20:01,560 --> 00:20:04,159
Speaker 6: The amplitude of the waves and the speed.

447
00:20:04,200 --> 00:20:07,480
Speaker 7: The timing of when the waves arrive is completely directly

448
00:20:07,520 --> 00:20:10,880
Speaker 7: related to the material properties that the waves traveled through.

449
00:20:11,240 --> 00:20:13,280
Speaker 7: So for example, we can figure out the density of

450
00:20:13,359 --> 00:20:16,679
Speaker 7: material that a wave traveled safe from. Let's say an

451
00:20:16,680 --> 00:20:20,159
Speaker 7: earthquake happens in California and the wave travels up to

452
00:20:21,520 --> 00:20:24,680
Speaker 7: Seattle in Washington. You can use that to figure out

453
00:20:24,760 --> 00:20:27,680
Speaker 7: kind of what's the material just under the surface there,

454
00:20:27,680 --> 00:20:30,040
Speaker 7: Whereas if you try to go across the globe to

455
00:20:30,080 --> 00:20:32,359
Speaker 7: another part on the other side, the waves might travel

456
00:20:32,359 --> 00:20:34,879
Speaker 7: through the entire planet, and we could actually sample the

457
00:20:34,920 --> 00:20:37,479
Speaker 7: material in the core, for example. So you can use

458
00:20:37,520 --> 00:20:40,040
Speaker 7: all those different measurements. The more locations you have on

459
00:20:40,080 --> 00:20:42,280
Speaker 7: the Earth for these seismic measurements to be made, the

460
00:20:42,320 --> 00:20:45,160
Speaker 7: more you can kind of discern what is the lateral

461
00:20:45,200 --> 00:20:46,960
Speaker 7: structure of the interior of the Earth.

462
00:20:47,040 --> 00:20:49,080
Speaker 4: And we're really talking about sound waves, right, These are

463
00:20:49,119 --> 00:20:51,840
Speaker 4: pressure waves in the rock, and so we can think

464
00:20:51,880 --> 00:20:55,600
Speaker 4: about how denser materials have sound travel faster, and less

465
00:20:55,600 --> 00:20:58,560
Speaker 4: dense materials sound travels lower. So you're measuring the density

466
00:20:59,040 --> 00:21:01,000
Speaker 4: of the material by measure in the speed of sound.

467
00:21:01,240 --> 00:21:04,000
Speaker 4: But again, these are rocks that are like pushing on

468
00:21:04,040 --> 00:21:06,439
Speaker 4: each other, right, Like sound waves through rock is a

469
00:21:06,520 --> 00:21:07,960
Speaker 4: very weird thing to think about.

470
00:21:08,280 --> 00:21:10,399
Speaker 7: Yeah, absolutely, So there are the sound waves that The

471
00:21:10,440 --> 00:21:12,800
Speaker 7: other type of wave that goes through are these sheer waves.

472
00:21:12,800 --> 00:21:16,080
Speaker 7: So those are kind of more like waves you'd experience

473
00:21:16,119 --> 00:21:18,639
Speaker 7: in a fluid, let's say, or not in fluid, sorry,

474
00:21:18,640 --> 00:21:20,920
Speaker 7: waves that you would experience if you try to kind

475
00:21:20,920 --> 00:21:23,040
Speaker 7: of bend peanut butter or something like that. Right, So

476
00:21:23,040 --> 00:21:25,840
Speaker 7: there's multiple kinds of waves, and some of them are

477
00:21:26,640 --> 00:21:29,800
Speaker 7: very diagnostic of what's going on in certain types of materials.

478
00:21:29,960 --> 00:21:32,159
Speaker 4: Well, I never thought we'd be talking about peanut butter waves,

479
00:21:32,160 --> 00:21:34,840
Speaker 4: but here we are. So when did we get this picture? Like,

480
00:21:35,000 --> 00:21:37,159
Speaker 4: what is the first technique that really gave us a

481
00:21:37,240 --> 00:21:39,439
Speaker 4: view of the inside of the Earth. Was it the

482
00:21:39,520 --> 00:21:41,359
Speaker 4: seismographs or is it something else?

483
00:21:41,640 --> 00:21:42,600
Speaker 6: That's a good question.

484
00:21:42,840 --> 00:21:45,119
Speaker 7: It's not like there was a moment where suddenly we

485
00:21:45,119 --> 00:21:47,040
Speaker 7: had this picture of the Earth. I think we developed

486
00:21:47,119 --> 00:21:50,840
Speaker 7: our understanding to higher and higher precision as time went on, Right,

487
00:21:50,920 --> 00:21:53,720
Speaker 7: I think early studies of gravity, going back to Newton,

488
00:21:53,840 --> 00:21:56,040
Speaker 7: let's say, was able to tell us this is the

489
00:21:56,080 --> 00:21:58,120
Speaker 7: mass of the Earth, and then you could take, for example,

490
00:21:58,160 --> 00:22:00,480
Speaker 7: samples of crustal rocks and figure out what they're density

491
00:22:00,600 --> 00:22:02,760
Speaker 7: was and infer hey, there must be a lot more

492
00:22:02,800 --> 00:22:04,760
Speaker 7: mass deeper in the center. So that was kind of

493
00:22:05,000 --> 00:22:08,560
Speaker 7: first order information you might get so through both seismology.

494
00:22:08,680 --> 00:22:10,919
Speaker 7: So early nineteen hundreds was when we were doing some

495
00:22:10,920 --> 00:22:14,240
Speaker 7: really great seismology figuring out things like, oh, look we

496
00:22:14,320 --> 00:22:16,320
Speaker 7: have a core. Right, that was where the core was

497
00:22:16,320 --> 00:22:18,600
Speaker 7: first discovered. The inner core was discovered in the early

498
00:22:18,640 --> 00:22:22,080
Speaker 7: nineteen hundreds. The first sort of real profile of density

499
00:22:22,119 --> 00:22:24,359
Speaker 7: through the Earth happened, I think it was in the

500
00:22:24,400 --> 00:22:27,240
Speaker 7: seventies with what was called the Preliminary Reference Earth Model,

501
00:22:27,480 --> 00:22:30,040
Speaker 7: which really used a whole bunch of seismic data to

502
00:22:30,160 --> 00:22:32,200
Speaker 7: really kind of do an inverse problem and figure out,

503
00:22:32,480 --> 00:22:34,919
Speaker 7: here's what the seismic wave speed and the density has

504
00:22:34,960 --> 00:22:36,840
Speaker 7: to be at every depth in the in sort of

505
00:22:36,840 --> 00:22:37,760
Speaker 7: like a onon d Earth.

506
00:22:37,840 --> 00:22:40,240
Speaker 6: So that was a big step forward there too.

507
00:22:40,560 --> 00:22:42,960
Speaker 7: But at the same time gravity was being used and

508
00:22:43,000 --> 00:22:45,720
Speaker 7: so we were getting pictures from different types of information.

509
00:22:46,000 --> 00:22:48,040
Speaker 4: But it's really only a few hundred years that we've

510
00:22:48,040 --> 00:22:50,600
Speaker 4: had any sort of reasonable idea of what's under our feet.

511
00:22:50,640 --> 00:22:52,920
Speaker 4: And it sounds like only the last few decades, maybe

512
00:22:52,920 --> 00:22:55,800
Speaker 4: fifty years, that we've had any sort of detailed picture

513
00:22:55,880 --> 00:22:58,680
Speaker 4: of what's actually inside our own planet. It's incredible how

514
00:22:58,720 --> 00:23:02,280
Speaker 4: long we can remain ignorant about really basic science about

515
00:23:02,280 --> 00:23:03,000
Speaker 4: our own lives.

516
00:23:03,200 --> 00:23:06,600
Speaker 7: Yeah, when I talk to people, I tell them geophysics

517
00:23:06,760 --> 00:23:09,280
Speaker 7: is really modern physics because all of the stuff we're

518
00:23:09,320 --> 00:23:11,359
Speaker 7: doing now is all stuff that's happened sort of in

519
00:23:11,400 --> 00:23:12,840
Speaker 7: the last sixty seventy years.

520
00:23:12,840 --> 00:23:15,639
Speaker 6: So I like to think of it as a modern physics.

521
00:23:15,280 --> 00:23:19,240
Speaker 4: Approach, right, And now we've extended this frontier too other planets.

522
00:23:19,280 --> 00:23:21,520
Speaker 4: We've talked in the podcast before about the Insight mission,

523
00:23:21,560 --> 00:23:24,160
Speaker 4: and I think you worked on that measuring Mars quakes

524
00:23:24,200 --> 00:23:27,920
Speaker 4: to see what's inside Mars. Did the same principles apply there?

525
00:23:28,040 --> 00:23:29,080
Speaker 6: Yes, absolutely, So.

526
00:23:29,119 --> 00:23:32,359
Speaker 7: The amazing thing with the Insite mission is brought a

527
00:23:32,400 --> 00:23:35,280
Speaker 7: seismometer and that seismometer had to be placed onto the

528
00:23:35,280 --> 00:23:38,200
Speaker 7: surface of Mars so that it could measure the ground

529
00:23:38,240 --> 00:23:41,280
Speaker 7: shaking essentially, and it worked, like it was just amazing

530
00:23:41,280 --> 00:23:43,480
Speaker 7: that it worked. But it was a very interesting experience

531
00:23:43,520 --> 00:23:47,080
Speaker 7: because for most of the mission, and especially in the beginning,

532
00:23:47,720 --> 00:23:50,639
Speaker 7: all the Mars quakes we were seeing were quite weak.

533
00:23:51,000 --> 00:23:52,760
Speaker 7: We were looking for the big one, right, We're looking

534
00:23:52,760 --> 00:23:55,160
Speaker 7: for the big Mars quake, because the bigger the quake,

535
00:23:55,400 --> 00:23:58,080
Speaker 7: the more ways we'll travel through the deeper parts of Mars.

536
00:23:58,080 --> 00:24:00,000
Speaker 7: And so we really wanted to study or I really

537
00:24:00,080 --> 00:24:02,280
Speaker 7: wanted to study the core, and for that we needed

538
00:24:02,280 --> 00:24:04,320
Speaker 7: some big Mars quakes. And they really didn't happen for

539
00:24:04,359 --> 00:24:06,399
Speaker 7: the first few years, and then right near when the

540
00:24:06,520 --> 00:24:08,960
Speaker 7: mission was about to end, we suddenly had a few.

541
00:24:09,000 --> 00:24:10,959
Speaker 6: So that was really amazing to get that data at

542
00:24:10,960 --> 00:24:12,840
Speaker 6: the end. So Mars kind of kept us hoping for

543
00:24:12,880 --> 00:24:14,320
Speaker 6: a while and then finally delivered.

544
00:24:14,520 --> 00:24:17,040
Speaker 4: And before you landed on Mars with this seismometer, did

545
00:24:17,040 --> 00:24:20,280
Speaker 4: you have much reason to expect that there were Mars quakes?

546
00:24:20,440 --> 00:24:22,719
Speaker 4: Or it could be that Mars was totally silent.

547
00:24:22,880 --> 00:24:24,520
Speaker 7: I mean it could have been we didn't have any

548
00:24:24,520 --> 00:24:27,560
Speaker 7: direct evidence from marsquakes. But my geologist friends who are

549
00:24:27,640 --> 00:24:30,119
Speaker 7: used to looking at say, tectonic features on the surface,

550
00:24:30,160 --> 00:24:32,280
Speaker 7: looking at things like where are the cracks in the surface,

551
00:24:32,320 --> 00:24:34,280
Speaker 7: where are the mountains, they would have told me to

552
00:24:34,320 --> 00:24:36,360
Speaker 7: expect Mars quakes because.

553
00:24:36,119 --> 00:24:39,120
Speaker 6: They see movements geologically.

554
00:24:38,400 --> 00:24:41,399
Speaker 7: They see movements on the surface. But also, luckily, we

555
00:24:41,520 --> 00:24:44,000
Speaker 7: kind of have our own source of Mars quakes. In

556
00:24:44,040 --> 00:24:48,400
Speaker 7: a way, when meteors hit planets, they crash into them.

557
00:24:48,440 --> 00:24:52,120
Speaker 7: They're kind of like a hammer that's smashing into the bell, right,

558
00:24:52,359 --> 00:24:54,479
Speaker 7: And so a lot of the marsquakes we measured were

559
00:24:54,480 --> 00:24:57,000
Speaker 7: actually caused by meteors that hit Mars as opposed to

560
00:24:57,000 --> 00:24:59,240
Speaker 7: just tectonic activity happening in the interior.

561
00:24:59,280 --> 00:25:01,560
Speaker 4: Well, it's terrifle to me or feel a little conflicted

562
00:25:01,680 --> 00:25:05,119
Speaker 4: the geologists are rooting for quakes and rooting for like

563
00:25:05,160 --> 00:25:07,600
Speaker 4: big impacts because they're like, oh, yay data.

564
00:25:08,480 --> 00:25:11,440
Speaker 7: Yes exactly, I will I mean, as a funny story

565
00:25:11,600 --> 00:25:13,720
Speaker 7: on the mission, we did at one point, so the

566
00:25:13,720 --> 00:25:17,120
Speaker 7: Insight mission was on the surface when the Perseverance rover

567
00:25:17,560 --> 00:25:20,159
Speaker 7: was planning to land, and we did kind of do

568
00:25:20,200 --> 00:25:23,000
Speaker 7: a calculation where if the landing didn't go so well,

569
00:25:23,119 --> 00:25:24,640
Speaker 7: would be able to.

570
00:25:24,600 --> 00:25:27,919
Speaker 6: Detect away from that. Luckily that didn't happen. We had

571
00:25:27,920 --> 00:25:28,800
Speaker 6: a very nice landing.

572
00:25:28,920 --> 00:25:31,560
Speaker 4: Yeah, the congratulations on your landing. Too bad we didn't

573
00:25:31,560 --> 00:25:34,320
Speaker 4: get some cool data though from your explosion of your

574
00:25:34,440 --> 00:25:37,520
Speaker 4: huge project. Oh my gosh, all right, this is really

575
00:25:37,560 --> 00:25:39,480
Speaker 4: fun and I want to hear a lot more about

576
00:25:39,480 --> 00:25:42,480
Speaker 4: what's going on inside our planet. But first, let's take

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Speaker 4: Okay, we're back. We're talking to Professor Sabina Stanley, author

637
00:28:58,600 --> 00:29:01,600
Speaker 4: of the book What's Hidden in Side Planets about what's

638
00:29:01,720 --> 00:29:05,120
Speaker 4: inside our planet. You mentioned earlier that it was amazing

639
00:29:05,280 --> 00:29:07,760
Speaker 4: that Insight worked. Is that just because it's hard to

640
00:29:07,800 --> 00:29:10,440
Speaker 4: land stuff on Mars and operate a robot on another

641
00:29:10,480 --> 00:29:14,000
Speaker 4: planet or was there something particularly challenging about a seismometer

642
00:29:14,240 --> 00:29:15,040
Speaker 4: on another planet.

643
00:29:15,160 --> 00:29:18,120
Speaker 7: Yeah, Insight had a lot of firsts. I would say, right,

644
00:29:18,160 --> 00:29:20,400
Speaker 7: it wasn't the first lander. We've had other landers on

645
00:29:20,440 --> 00:29:22,160
Speaker 7: the surface, but this was the first time we were

646
00:29:22,160 --> 00:29:24,600
Speaker 7: going to take equipment that was stored on top of

647
00:29:24,640 --> 00:29:27,400
Speaker 7: the lander and actually physically move it to put it

648
00:29:27,440 --> 00:29:29,360
Speaker 7: on the surface. So there were lots of ways that

649
00:29:29,360 --> 00:29:31,720
Speaker 7: could have gone wrong. Right, This lander had this arm

650
00:29:32,160 --> 00:29:34,840
Speaker 7: type device that had to pick up the seismometer on

651
00:29:34,960 --> 00:29:38,360
Speaker 7: the lander and move it onto the surface, So that

652
00:29:38,480 --> 00:29:41,520
Speaker 7: required tons of work to get that to just work properly.

653
00:29:41,520 --> 00:29:43,800
Speaker 7: Then it had to put a wind shield on top

654
00:29:43,880 --> 00:29:46,240
Speaker 7: of the seismometer to make sure that we didn't measure

655
00:29:46,240 --> 00:29:49,200
Speaker 7: a bunch of wind basically because wind also shakes schismometers.

656
00:29:50,000 --> 00:29:54,440
Speaker 7: Then you know, the seismometer wasn't the only instrument on insight.

657
00:29:54,600 --> 00:29:58,400
Speaker 7: There was also a thermal probe what we called the mole,

658
00:29:58,440 --> 00:30:02,400
Speaker 7: which was supposed to down about ten meters and take

659
00:30:02,440 --> 00:30:05,320
Speaker 7: temperature measurements at depth, which would have told us about

660
00:30:05,320 --> 00:30:08,160
Speaker 7: the heat flow coming out of Mars. Again, this was

661
00:30:08,200 --> 00:30:11,360
Speaker 7: going to be the first time anything like this was tried,

662
00:30:11,960 --> 00:30:15,040
Speaker 7: and unfortunately we couldn't get the mold to dig deeper

663
00:30:15,080 --> 00:30:19,840
Speaker 7: than about tens of centimeters. The properties of the soil

664
00:30:20,000 --> 00:30:22,240
Speaker 7: soils kind of word we use, but the properties of

665
00:30:22,320 --> 00:30:26,080
Speaker 7: the sand on Mars were not as we expected, and

666
00:30:26,280 --> 00:30:29,880
Speaker 7: just the device couldn't actually use friction to dig down

667
00:30:29,960 --> 00:30:30,760
Speaker 7: deeper and deeper.

668
00:30:30,800 --> 00:30:31,720
Speaker 6: So that was a struggle.

669
00:30:31,720 --> 00:30:35,719
Speaker 7: And we actually the insight engineering team that worked on

670
00:30:35,720 --> 00:30:37,480
Speaker 7: this and the scientists that worked on this, you know,

671
00:30:37,520 --> 00:30:39,440
Speaker 7: I wasn't part of this. It was just amazing the

672
00:30:39,480 --> 00:30:41,960
Speaker 7: things that they tried, and in the end we actually

673
00:30:41,960 --> 00:30:43,720
Speaker 7: did get some good science out of it. We measured

674
00:30:43,720 --> 00:30:45,600
Speaker 7: more sort of the thermal properties at the upper part

675
00:30:45,600 --> 00:30:48,320
Speaker 7: of the crust as opposed to deeper down. But it

676
00:30:48,360 --> 00:30:50,560
Speaker 7: was just amazing to see how much they tried to

677
00:30:50,600 --> 00:30:53,120
Speaker 7: work on doing this first digging on here. You know,

678
00:30:53,160 --> 00:30:55,120
Speaker 7: we talked about digging on the Earth is hard. Now

679
00:30:55,160 --> 00:30:58,040
Speaker 7: imagine digging on another planet without humans, and it's even

680
00:30:58,080 --> 00:30:59,120
Speaker 7: harder wonderful.

681
00:30:59,200 --> 00:31:01,160
Speaker 4: And then what are the plans for the future. Is

682
00:31:01,240 --> 00:31:04,360
Speaker 4: NASA planning to dig into the surfaces of any other

683
00:31:04,400 --> 00:31:07,840
Speaker 4: objects in the Solar System or put seismometers on any

684
00:31:07,840 --> 00:31:08,920
Speaker 4: other surfaces, So.

685
00:31:08,880 --> 00:31:11,880
Speaker 7: I think seismometers is definitely something that's going to go.

686
00:31:12,000 --> 00:31:14,120
Speaker 7: So there is a big push right now to send

687
00:31:14,160 --> 00:31:17,040
Speaker 7: spacecraft back to the Moon so that we can better

688
00:31:17,160 --> 00:31:21,360
Speaker 7: understand our closest celestial body, let's say. And so there

689
00:31:21,440 --> 00:31:23,880
Speaker 7: is a mission that will involve putting a seismometer, putting

690
00:31:23,880 --> 00:31:26,320
Speaker 7: more seismometers on the Moon. We already have some seismometers

691
00:31:26,360 --> 00:31:28,400
Speaker 7: on the Moon that we're turned off a while ago

692
00:31:28,480 --> 00:31:31,440
Speaker 7: for budgetary reasons, right, So it'll be great to get

693
00:31:31,480 --> 00:31:34,040
Speaker 7: seismology again on the Moon. But for me, the most

694
00:31:34,040 --> 00:31:37,960
Speaker 7: exciting is that an upcoming mission that's planned to go

695
00:31:38,040 --> 00:31:41,080
Speaker 7: to Titan, which is a moon of Saturn, is actually

696
00:31:41,080 --> 00:31:42,800
Speaker 7: going to have a seismometer on it as well. So

697
00:31:42,840 --> 00:31:45,080
Speaker 7: it'll be interesting to see what we can learn about

698
00:31:45,080 --> 00:31:47,040
Speaker 7: the interior of Titan.

699
00:31:46,880 --> 00:31:48,800
Speaker 4: And what do we know right now about the interior

700
00:31:48,800 --> 00:31:51,200
Speaker 4: of Titan, And how could we know anything about it

701
00:31:51,280 --> 00:31:53,520
Speaker 4: just from like looking at a few photons that happen

702
00:31:53,600 --> 00:31:54,400
Speaker 4: to reflect off of it.

703
00:31:54,600 --> 00:31:56,840
Speaker 7: So Titan is one of my favorite places. So it's

704
00:31:56,880 --> 00:31:58,440
Speaker 7: really exciting to think about what they're going to see.

705
00:31:58,480 --> 00:32:00,760
Speaker 7: So Titan's a unique place. First, well, it's the only

706
00:32:00,840 --> 00:32:03,560
Speaker 7: other planetary body in the Solar System that has a

707
00:32:03,680 --> 00:32:06,800
Speaker 7: nitrogen based atmosphere that's thick like the Earth's right, So

708
00:32:06,880 --> 00:32:11,040
Speaker 7: earth Is atmosphere is mostly nitrogen, and the surface pressure

709
00:32:11,080 --> 00:32:13,239
Speaker 7: on Titan is about one and a half bars, so

710
00:32:13,280 --> 00:32:15,360
Speaker 7: one and a half Earth atmospheres. But the cool thing

711
00:32:15,360 --> 00:32:18,000
Speaker 7: about Titan is that it's a small planet and so

712
00:32:18,040 --> 00:32:19,880
Speaker 7: it has very little mass and so its gravity is

713
00:32:19,920 --> 00:32:22,640
Speaker 7: really low. So if you were to go to Titan

714
00:32:22,960 --> 00:32:25,240
Speaker 7: and put some cardboard on your arms and flap them,

715
00:32:25,240 --> 00:32:27,200
Speaker 7: you would be able to fly on Titan because you

716
00:32:27,240 --> 00:32:31,480
Speaker 7: have ideal buoyancy situation there. You've got thick atmosphere, low gravity,

717
00:32:31,520 --> 00:32:33,080
Speaker 7: so it's really easy to fly there.

718
00:32:33,200 --> 00:32:35,640
Speaker 4: So in contrast, like they had the helicopter on Mars,

719
00:32:35,680 --> 00:32:37,760
Speaker 4: that was a real challenge because the atmosphere was thin

720
00:32:38,320 --> 00:32:41,600
Speaker 4: and the helicopter needs atmosphere exactly exactly.

721
00:32:42,120 --> 00:32:45,080
Speaker 7: So the Dragonfly mission, which is going to Titan should

722
00:32:45,120 --> 00:32:48,120
Speaker 7: get there in the mid twenty thirties. It is going

723
00:32:48,160 --> 00:32:50,960
Speaker 7: to involve a dual quad copter. So this thing has

724
00:32:51,000 --> 00:32:55,600
Speaker 7: basically eight rotors and this to me, because I'm Canadian,

725
00:32:55,640 --> 00:32:58,080
Speaker 7: it looks like a skidew or a snowmobile because it

726
00:32:58,080 --> 00:33:02,000
Speaker 7: has these sled track treks underneath it. But it's basically

727
00:33:02,040 --> 00:33:04,920
Speaker 7: going to fly around land somewhere, do a bunch of science,

728
00:33:05,280 --> 00:33:08,920
Speaker 7: then take off again, look for a new location, scout somewhat,

729
00:33:09,080 --> 00:33:10,880
Speaker 7: then fly to a new location, land again. And so

730
00:33:10,920 --> 00:33:14,280
Speaker 7: it's going to be able to do ground local science

731
00:33:14,360 --> 00:33:16,840
Speaker 7: right at an individual location for a bunch of locations

732
00:33:16,840 --> 00:33:19,760
Speaker 7: over the surface. And that's really the challenge in planetary

733
00:33:19,760 --> 00:33:22,720
Speaker 7: science is this kind of combination of get lots of

734
00:33:22,800 --> 00:33:26,000
Speaker 7: data from lots of different places, really locally, really close

735
00:33:26,040 --> 00:33:26,520
Speaker 7: to the surface.

736
00:33:26,520 --> 00:33:28,080
Speaker 6: So that's going to be a very exciting mission.

737
00:33:28,280 --> 00:33:29,920
Speaker 4: We'd have to ask you about that. Is that going

738
00:33:29,960 --> 00:33:32,000
Speaker 4: to be self directed? Is it going to decide on

739
00:33:32,080 --> 00:33:33,520
Speaker 4: its own where to go? Or is it going to

740
00:33:33,680 --> 00:33:36,720
Speaker 4: wait for signals for minutes and minutes from Earth?

741
00:33:36,920 --> 00:33:39,680
Speaker 7: Full disclosure here, I have no involvement in the Dragonfly mission.

742
00:33:39,680 --> 00:33:42,400
Speaker 7: I'm just a super fan. But my understanding is what

743
00:33:42,400 --> 00:33:44,800
Speaker 7: it's going to do is when it kind of goes

744
00:33:44,960 --> 00:33:47,000
Speaker 7: up the one time. When it flies up one time,

745
00:33:47,040 --> 00:33:49,360
Speaker 7: it's going to survey, it's going to look around. Then

746
00:33:49,400 --> 00:33:52,720
Speaker 7: it'll come back down recharge its batteries. And during that time,

747
00:33:52,800 --> 00:33:54,520
Speaker 7: when the data gets back to Earth, people are going

748
00:33:54,560 --> 00:33:57,120
Speaker 7: to look around and say, let's go here, right that

749
00:33:57,200 --> 00:33:58,680
Speaker 7: place over there looks kind of interesting.

750
00:33:58,720 --> 00:34:02,080
Speaker 6: So it'll be a combination. Some of the in time flight.

751
00:34:01,800 --> 00:34:04,280
Speaker 7: Stuff is going to have to be done by the

752
00:34:04,280 --> 00:34:06,640
Speaker 7: spacecraft by itself, but when it comes to making decisions

753
00:34:06,640 --> 00:34:08,560
Speaker 7: about where to go next in terms of big steps,

754
00:34:09,000 --> 00:34:10,319
Speaker 7: that's going to be done by the people back.

755
00:34:10,239 --> 00:34:10,719
Speaker 6: Your on Earth.

756
00:34:10,719 --> 00:34:14,000
Speaker 4: I really liked your comment about needing to sample several places.

757
00:34:14,280 --> 00:34:16,399
Speaker 4: It seems obvious that if you only land on Earth

758
00:34:16,400 --> 00:34:18,800
Speaker 4: in one place, you might conclude, oh, this whole place

759
00:34:18,840 --> 00:34:21,880
Speaker 4: is grantede or oh look it's all beautiful marble or something.

760
00:34:22,040 --> 00:34:24,880
Speaker 4: Obviously you need to look around to get a better sample.

761
00:34:25,200 --> 00:34:27,040
Speaker 4: And so when we only land on one place on

762
00:34:27,080 --> 00:34:29,760
Speaker 4: the Moon, like the Apollo astronauts, you know, only looked

763
00:34:29,920 --> 00:34:32,759
Speaker 4: or near where they landed, we may have gotten to

764
00:34:32,760 --> 00:34:34,719
Speaker 4: bia a sample of what's going on up there. So

765
00:34:34,960 --> 00:34:37,200
Speaker 4: that's really cool that they're going to explore it. So

766
00:34:37,280 --> 00:34:39,440
Speaker 4: other than landing on the surface. In your book, you

767
00:34:39,440 --> 00:34:42,800
Speaker 4: were talking about seeing what's inside a planet by basically

768
00:34:42,800 --> 00:34:45,160
Speaker 4: how it wobbles. Can you walk us through the physics

769
00:34:45,160 --> 00:34:47,200
Speaker 4: of that, the moment of inertia, and how it gives

770
00:34:47,239 --> 00:34:48,600
Speaker 4: us a picture of what's inside.

771
00:34:48,960 --> 00:34:49,240
Speaker 6: Yeah.

772
00:34:49,280 --> 00:34:53,360
Speaker 7: Absolutely, So all of the planets spin to some amount, right,

773
00:34:53,440 --> 00:34:55,480
Speaker 7: That's why we have a day on the Earth. And

774
00:34:56,719 --> 00:35:00,400
Speaker 7: when it spins, a planet doesn't just stay a perfect sphere.

775
00:35:00,440 --> 00:35:02,600
Speaker 7: It kind of gets fatter at the equator than it

776
00:35:02,600 --> 00:35:04,879
Speaker 7: does at the poles. Now, it turns out that how

777
00:35:04,920 --> 00:35:07,400
Speaker 7: fat it gets at the equator versus the poles is

778
00:35:07,440 --> 00:35:10,799
Speaker 7: directly related to what the material properties of the object are. So,

779
00:35:10,840 --> 00:35:12,719
Speaker 7: for example, if you had a perfect water planet, right,

780
00:35:12,760 --> 00:35:15,000
Speaker 7: imagine the small planet made of water and you spun it,

781
00:35:15,080 --> 00:35:17,960
Speaker 7: there's a specific like ellipsoidal shape you would get for

782
00:35:18,040 --> 00:35:21,000
Speaker 7: a liquid planet, Whereas if you had a dense core

783
00:35:21,239 --> 00:35:23,799
Speaker 7: inside the planet and with a solid layer and then

784
00:35:23,840 --> 00:35:26,000
Speaker 7: a water ocean on the outside, you're going to get

785
00:35:26,040 --> 00:35:28,680
Speaker 7: a different amount of flattening or a different amount of

786
00:35:28,800 --> 00:35:31,120
Speaker 7: kind of bulging at the equator. From that, so we

787
00:35:31,160 --> 00:35:33,920
Speaker 7: can actually use the amount of bulging of these planets

788
00:35:34,200 --> 00:35:38,080
Speaker 7: when they're spinning to get information about what's inside.

789
00:35:38,200 --> 00:35:40,920
Speaker 4: So, for example, you spin a basketball, it stays a sphere,

790
00:35:40,960 --> 00:35:43,200
Speaker 4: But if you spin a blob of pizza dough, it

791
00:35:43,280 --> 00:35:46,000
Speaker 4: becomes a disc, right, and so it tells you pizza

792
00:35:46,040 --> 00:35:48,680
Speaker 4: dough softer than basketballs. I guess we already knew that,

793
00:35:48,680 --> 00:35:50,800
Speaker 4: But you're saying, we can apply the same thing to planets.

794
00:35:50,960 --> 00:35:53,560
Speaker 4: By the deformation of the sphere, we can tell basically

795
00:35:53,560 --> 00:35:54,480
Speaker 4: how rigid it is.

796
00:35:54,680 --> 00:35:57,239
Speaker 7: Yes, absolutely, and also where the dense, how dense it

797
00:35:57,320 --> 00:36:01,640
Speaker 7: is essentially in different parts. So for example, Saturn, Saturn

798
00:36:01,760 --> 00:36:04,160
Speaker 7: is the bulgiest of all the planets in our solar systems.

799
00:36:04,160 --> 00:36:06,080
Speaker 7: Even if you look at through a telescope, it doesn't

800
00:36:06,080 --> 00:36:08,680
Speaker 7: look like a sphere. It actually looks like more of

801
00:36:08,719 --> 00:36:11,839
Speaker 7: an oblate spheroid. So it's really interesting to look at

802
00:36:11,840 --> 00:36:12,920
Speaker 7: Saturn through a telescope.

803
00:36:13,000 --> 00:36:15,480
Speaker 4: You mean Saturn looks like squished, like somebody sat on it.

804
00:36:15,600 --> 00:36:17,600
Speaker 6: Yes, Saturn looks like someone satur on it.

805
00:36:17,480 --> 00:36:20,080
Speaker 4: In the best possible way. I mean Saturn's beautiful, yes.

806
00:36:20,040 --> 00:36:23,000
Speaker 7: Yes, absolutely, But because of that we know that Saturn

807
00:36:23,120 --> 00:36:25,880
Speaker 7: isn't just a ball of hydrogen helium. We know that

808
00:36:25,880 --> 00:36:28,800
Speaker 7: there have to be some rocks inside kind of condensed

809
00:36:28,880 --> 00:36:31,600
Speaker 7: at the center, and then the gas sphere is kind

810
00:36:31,640 --> 00:36:33,320
Speaker 7: of more on the outside of it. So we've actually

811
00:36:33,320 --> 00:36:35,239
Speaker 7: been able to figure that out from the size of

812
00:36:35,280 --> 00:36:36,560
Speaker 7: its equatorial bulge.

813
00:36:36,680 --> 00:36:38,560
Speaker 6: So that's the first way we can use rotation. There

814
00:36:38,600 --> 00:36:39,200
Speaker 6: are other ways.

815
00:36:39,239 --> 00:36:43,160
Speaker 7: So for example, as planets orbit and rotate, they can

816
00:36:43,440 --> 00:36:46,839
Speaker 7: actually as they're rotating, they don't always point their north

817
00:36:46,840 --> 00:36:50,400
Speaker 7: pole to exactly the same location, so they can actually process,

818
00:36:50,440 --> 00:36:53,920
Speaker 7: so their rotational axis can move around in a circle

819
00:36:54,239 --> 00:36:56,560
Speaker 7: about their orbit axis. And if you've ever played with

820
00:36:56,680 --> 00:36:59,040
Speaker 7: like a top, like a toy top, and you've spun

821
00:36:59,080 --> 00:37:01,800
Speaker 7: it and you've seen it make this little wobbly circlar pattern,

822
00:37:01,880 --> 00:37:04,880
Speaker 7: planets do the same thing. So planetary rotation axis wobble.

823
00:37:04,920 --> 00:37:07,160
Speaker 7: They process, and they also do this thing called nutating

824
00:37:07,160 --> 00:37:10,080
Speaker 7: where they kind of dip down a little bit, And

825
00:37:10,280 --> 00:37:14,080
Speaker 7: the period of those procession motions and the kind of

826
00:37:14,080 --> 00:37:17,800
Speaker 7: how cyclical they are really tells us about the interior

827
00:37:17,840 --> 00:37:18,680
Speaker 7: properties as well.

828
00:37:18,719 --> 00:37:20,359
Speaker 4: But why does it happen in the first place, I mean,

829
00:37:20,440 --> 00:37:23,360
Speaker 4: does an angular momentum tell us that it should we

830
00:37:23,440 --> 00:37:25,840
Speaker 4: spin along the same axis. Is this the effect of

831
00:37:25,920 --> 00:37:27,480
Speaker 4: like other things pulling on it?

832
00:37:27,719 --> 00:37:28,520
Speaker 6: Yes, exactly.

833
00:37:28,640 --> 00:37:31,200
Speaker 7: So if Earth were alone, if it was just the Earth,

834
00:37:31,239 --> 00:37:33,040
Speaker 7: then nothing else was around, we would not have any

835
00:37:33,040 --> 00:37:36,959
Speaker 7: procession or nutation. But we've got the Sun, we've got

836
00:37:37,000 --> 00:37:40,440
Speaker 7: the moon nearby, and both of those things causecessional motions

837
00:37:40,440 --> 00:37:44,040
Speaker 7: and wobbling nutational motions that affect our orbit in our day.

838
00:37:44,280 --> 00:37:46,719
Speaker 4: So Jupiter and the other things are pulling on the

839
00:37:46,760 --> 00:37:50,080
Speaker 4: Earth and changing the direction of its spin axis basically

840
00:37:50,200 --> 00:37:53,040
Speaker 4: like where the north pole is pointing in the galaxy,

841
00:37:53,680 --> 00:37:56,280
Speaker 4: And you're saying that tells us something about what's inside

842
00:37:56,280 --> 00:37:58,400
Speaker 4: the Earth. People I think are used to thinking about

843
00:37:58,400 --> 00:38:00,520
Speaker 4: the gravitational model of like, well, you can treat the

844
00:38:00,520 --> 00:38:03,000
Speaker 4: whole planet as a point mass at its center of mass,

845
00:38:03,200 --> 00:38:05,040
Speaker 4: you can't learn anything else about it. So how is

846
00:38:05,080 --> 00:38:07,680
Speaker 4: it possible to know something about the distribution of mass

847
00:38:07,719 --> 00:38:10,320
Speaker 4: inside the planet from how it's spin wobbles.

848
00:38:10,480 --> 00:38:13,040
Speaker 7: So the wobbling and the spin can tell you things,

849
00:38:13,040 --> 00:38:15,120
Speaker 7: for example, like if you have a liquid layer inside

850
00:38:15,120 --> 00:38:17,000
Speaker 7: the planet. So I don't know if you've ever played

851
00:38:17,000 --> 00:38:19,560
Speaker 7: this game, but if you take a beach ball and

852
00:38:19,600 --> 00:38:22,000
Speaker 7: you put like a little pocket of water in it,

853
00:38:22,080 --> 00:38:23,760
Speaker 7: and you try to throw it to someone, it moves

854
00:38:23,760 --> 00:38:26,879
Speaker 7: completely differently than if you don't, or even easier, take

855
00:38:26,880 --> 00:38:30,479
Speaker 7: an egg, Take a raw egg and take a cooked egg,

856
00:38:30,560 --> 00:38:32,680
Speaker 7: both still in their shells, and put them on your

857
00:38:32,680 --> 00:38:34,680
Speaker 7: counter and spin them, and you will see that they

858
00:38:34,760 --> 00:38:37,720
Speaker 7: spin very differently because one of them has liquids inside

859
00:38:37,760 --> 00:38:39,960
Speaker 7: of it and the other one is fully solid. So

860
00:38:40,000 --> 00:38:43,840
Speaker 7: we can use the way that the spin axis wobbles

861
00:38:44,040 --> 00:38:46,320
Speaker 7: to figure out where are there liquid layers in this planet?

862
00:38:46,360 --> 00:38:48,959
Speaker 7: Is it fully solid that sort of thing I see?

863
00:38:49,400 --> 00:38:51,680
Speaker 4: Is this planet more like a soft or hard boiled egg.

864
00:38:52,920 --> 00:38:56,160
Speaker 4: That's incredible, And can't you also measure the moment of

865
00:38:56,160 --> 00:38:58,560
Speaker 4: inertia of the planet and tell like where the mass

866
00:38:58,640 --> 00:39:00,640
Speaker 4: is distributed, and like you can tell the difference between

867
00:39:01,040 --> 00:39:03,279
Speaker 4: like all the mass being at the core versus all

868
00:39:03,320 --> 00:39:04,720
Speaker 4: the mass being at the surface.

869
00:39:05,080 --> 00:39:07,279
Speaker 7: Yeah, so it's a bit complicated in the math, but

870
00:39:07,320 --> 00:39:09,960
Speaker 7: it turns out that the procession rate, so how fast

871
00:39:10,320 --> 00:39:13,960
Speaker 7: the axis of the rotation processes about the orbit normal.

872
00:39:14,000 --> 00:39:14,880
Speaker 6: I'll give you any example.

873
00:39:14,920 --> 00:39:17,120
Speaker 7: So on the Earth, right now, our north pole points

874
00:39:17,120 --> 00:39:19,080
Speaker 7: to the North Star. It was named that way for

875
00:39:19,120 --> 00:39:21,840
Speaker 7: a very specific reason. But it's moving around and in

876
00:39:21,840 --> 00:39:24,600
Speaker 7: about twenty It takes about twenty six thousand years for

877
00:39:24,680 --> 00:39:25,560
Speaker 7: that pole to.

878
00:39:25,520 --> 00:39:26,719
Speaker 6: Get back to the North Star.

879
00:39:27,280 --> 00:39:30,680
Speaker 7: Right, So the period of our orbit is twenty six

880
00:39:30,719 --> 00:39:34,680
Speaker 7: thousand years, and that period can be used to actually

881
00:39:35,320 --> 00:39:38,239
Speaker 7: determine the moment of inertia of the Earth through some

882
00:39:38,520 --> 00:39:41,719
Speaker 7: fancy math formulas. And so if we can measure the

883
00:39:41,719 --> 00:39:44,920
Speaker 7: precession rate or the period for other planetary bodies, we

884
00:39:44,920 --> 00:39:46,919
Speaker 7: can also figure out their moment of inertia.

885
00:39:47,000 --> 00:39:50,160
Speaker 4: Wow, twenty six thousand years? How long have we been

886
00:39:50,200 --> 00:39:53,040
Speaker 4: making these measurements? Couldn't be more than a thousand years

887
00:39:53,080 --> 00:39:53,719
Speaker 4: at maximum?

888
00:39:53,840 --> 00:39:56,279
Speaker 7: Yeah, yeah, it's definitely less than that. But you know,

889
00:39:56,320 --> 00:39:57,920
Speaker 7: you can you can trace out a little arc of

890
00:39:57,920 --> 00:39:59,680
Speaker 7: a circle, then you can pretty much draw out the

891
00:39:59,680 --> 00:40:00,480
Speaker 7: rest of the circle.

892
00:40:00,640 --> 00:40:02,160
Speaker 4: Yeah, I guess we have a model and we can

893
00:40:02,200 --> 00:40:05,359
Speaker 4: fit to that little arc. That's amazing, incredible. We can

894
00:40:05,440 --> 00:40:08,680
Speaker 4: learn so much about what's inside these objects without even

895
00:40:08,719 --> 00:40:11,160
Speaker 4: ever going inside. All right, I can't wait to talk

896
00:40:11,239 --> 00:40:13,080
Speaker 4: about this the more, but first we have to take

897
00:40:13,239 --> 00:40:13,960
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898
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901
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948
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Speaker 4: Okay, we're back and we're talking to Professor Sabina Stanley,

949
00:43:00,120 --> 00:43:03,200
Speaker 4: the author of the new book What's Hidden Inside Planets

950
00:43:03,280 --> 00:43:06,160
Speaker 4: about what's inside the Earth and other planets. Now, I

951
00:43:06,200 --> 00:43:08,800
Speaker 4: want to talk about sort of how the inside affects

952
00:43:08,800 --> 00:43:12,120
Speaker 4: the outside, because obviously, if you're just curious about how

953
00:43:12,120 --> 00:43:14,080
Speaker 4: the Solar system is formed, you want to know what's

954
00:43:14,080 --> 00:43:16,920
Speaker 4: inside the Earth. But even if you're not, like it

955
00:43:16,960 --> 00:43:20,200
Speaker 4: has an effect on living on the surface, right, tell

956
00:43:20,280 --> 00:43:23,040
Speaker 4: us about, like how the magnetic field of these things

957
00:43:23,160 --> 00:43:25,680
Speaker 4: is generated and how it relates to bubbling soup.

958
00:43:25,920 --> 00:43:28,520
Speaker 6: Yeah, so magnetic fields are my favorite topic. Not going

959
00:43:28,600 --> 00:43:30,440
Speaker 6: to lie. So here's this amazing thing.

960
00:43:30,520 --> 00:43:32,520
Speaker 7: Right, We're on the surface of the Earth, and one

961
00:43:32,520 --> 00:43:34,560
Speaker 7: of the reasons it's such a nice place to live

962
00:43:34,600 --> 00:43:37,280
Speaker 7: at the moment is because we have this beautiful magnetic

963
00:43:37,320 --> 00:43:40,760
Speaker 7: field that completely envelops the Earth. And that magnetic field,

964
00:43:40,840 --> 00:43:43,200
Speaker 7: what it does for us is it shields the surface

965
00:43:43,280 --> 00:43:45,680
Speaker 7: from high energy particles that come from the solar wind

966
00:43:45,719 --> 00:43:47,960
Speaker 7: which come from the Sun, and from cosmic rays that

967
00:43:48,000 --> 00:43:51,040
Speaker 7: come from deep space, and those very high energy particles.

968
00:43:51,160 --> 00:43:53,480
Speaker 7: If we didn't have our magnetic field, they would kind

969
00:43:53,520 --> 00:43:55,600
Speaker 7: of blast the surface of the Earth and they would

970
00:43:55,640 --> 00:43:57,759
Speaker 7: do some terrible things. First of all, they would cause

971
00:43:57,840 --> 00:44:01,120
Speaker 7: high radiation environments, so we'd likely have high rates of cancer,

972
00:44:01,200 --> 00:44:05,560
Speaker 7: for example. But also they cause lots of electrical disturbances,

973
00:44:05,600 --> 00:44:07,719
Speaker 7: and if you think about our power grid, our power

974
00:44:07,719 --> 00:44:10,160
Speaker 7: grid does not like there to be large fluctuations in

975
00:44:10,239 --> 00:44:13,920
Speaker 7: electromagnetic fields. That's another thing that is not so good.

976
00:44:14,080 --> 00:44:18,759
Speaker 7: It also tends to these solar winds that bombard planets.

977
00:44:19,040 --> 00:44:22,080
Speaker 7: They can actually erode the atmosphere of a planet, so

978
00:44:22,120 --> 00:44:24,319
Speaker 7: they can take they can basically, you know, it's like

979
00:44:24,400 --> 00:44:26,520
Speaker 7: pointing a hair dryer at the Earth. You're going to

980
00:44:26,520 --> 00:44:28,160
Speaker 7: be able to blow off all the gas from it.

981
00:44:28,480 --> 00:44:30,279
Speaker 7: So there are all these things that the magnetic field

982
00:44:30,280 --> 00:44:33,320
Speaker 7: actually shields us from. But this magnetic field that surrounds

983
00:44:33,400 --> 00:44:36,440
Speaker 7: us is actually created deep inside the Earth in the

984
00:44:36,480 --> 00:44:41,000
Speaker 7: iron core. So iron is great electrical conductor. When you

985
00:44:41,000 --> 00:44:43,040
Speaker 7: have a great electrical conductor, if you can get it

986
00:44:43,080 --> 00:44:46,040
Speaker 7: moving around in the right way, then you can actually

987
00:44:46,120 --> 00:44:49,719
Speaker 7: generate magnetic fields. And the best kind of analogy I

988
00:44:49,719 --> 00:44:51,360
Speaker 7: can think of for this is if anyone has a

989
00:44:51,360 --> 00:44:54,880
Speaker 7: home generator or if they have a bike light that

990
00:44:54,920 --> 00:44:57,840
Speaker 7: they can pedal to get going, you're basically converting the

991
00:44:57,920 --> 00:45:01,560
Speaker 7: kinetic energy of that motion into electromagnetic energy. So you

992
00:45:01,640 --> 00:45:04,560
Speaker 7: either you know you're pedaling, causes your bike light, causes

993
00:45:04,600 --> 00:45:07,640
Speaker 7: currents to flow that causes your bike light to shine right,

994
00:45:07,800 --> 00:45:11,200
Speaker 7: or similar in your generator. So in the core of

995
00:45:11,239 --> 00:45:15,320
Speaker 7: the earth, convection which occurs because the center is hotter

996
00:45:15,680 --> 00:45:17,799
Speaker 7: than the outer parts of the core, so you kind

997
00:45:17,800 --> 00:45:19,600
Speaker 7: of have bubbling up like like you would if you

998
00:45:19,600 --> 00:45:21,480
Speaker 7: put a pot of soup on the stove, right, you

999
00:45:21,560 --> 00:45:24,040
Speaker 7: get the bottom of the pot is hot, the top

1000
00:45:24,080 --> 00:45:26,920
Speaker 7: of the pot is cold, So you get these overturning

1001
00:45:26,960 --> 00:45:30,000
Speaker 7: motions in the soup. Same thing happens in the core,

1002
00:45:30,280 --> 00:45:33,680
Speaker 7: and so that overturning motions they create magnetic fields and

1003
00:45:33,880 --> 00:45:36,520
Speaker 7: you get what called a dynamo. So the dynamo in

1004
00:45:36,560 --> 00:45:38,560
Speaker 7: the center of the Earth generates this magnetic field that

1005
00:45:38,600 --> 00:45:39,880
Speaker 7: protects us on the surface.

1006
00:45:40,080 --> 00:45:43,520
Speaker 4: Amazing, and so you're saying that it's the convection cells

1007
00:45:43,760 --> 00:45:46,800
Speaker 4: that generate the magnetic field, not, for example, the spinning

1008
00:45:46,840 --> 00:45:47,400
Speaker 4: of the planet.

1009
00:45:47,800 --> 00:45:52,560
Speaker 7: Right, So there is a somewhat common misunderstanding out there

1010
00:45:52,960 --> 00:45:55,200
Speaker 7: that the reason that Earth has a magnetic field, for example,

1011
00:45:55,239 --> 00:45:58,040
Speaker 7: is due to its spinning, And this has been used sometimes,

1012
00:45:58,040 --> 00:46:01,640
Speaker 7: for example, to explain why Vna, which is spinning very slowly,

1013
00:46:02,080 --> 00:46:04,279
Speaker 7: doesn't have a magnetic field. And it turns out that

1014
00:46:04,320 --> 00:46:07,880
Speaker 7: you don't need spinning at all to generate a magnetic field.

1015
00:46:07,960 --> 00:46:12,200
Speaker 7: So magnetic fields can be generated through dynamo processes without spinning. Now,

1016
00:46:12,239 --> 00:46:15,920
Speaker 7: spinning sometimes helps in organizing motions and stuff like that,

1017
00:46:16,080 --> 00:46:19,120
Speaker 7: but it's not actually a requirement. So it's the convective motions,

1018
00:46:19,160 --> 00:46:20,240
Speaker 7: not the spinning, right.

1019
00:46:20,400 --> 00:46:22,880
Speaker 4: And so in your analogy, you're talking about like peddling

1020
00:46:23,080 --> 00:46:26,359
Speaker 4: your bicycle to generate electricity, And we haven't seen any

1021
00:46:26,400 --> 00:46:29,160
Speaker 4: magnetic monopoles in our universe, so we know that to

1022
00:46:29,239 --> 00:46:31,600
Speaker 4: generate magnetic fields you have to take a charge and

1023
00:46:31,680 --> 00:46:34,680
Speaker 4: put it in motion, which is how electrical generators work.

1024
00:46:34,800 --> 00:46:38,160
Speaker 4: But what is the charge here? Like we have flows

1025
00:46:38,200 --> 00:46:41,040
Speaker 4: of iron. Iron is obviously metallic and it conducts, but

1026
00:46:41,280 --> 00:46:44,000
Speaker 4: don't you need some ion in motion in order to

1027
00:46:44,000 --> 00:46:46,480
Speaker 4: get a current going? What generates the actual current? If

1028
00:46:46,520 --> 00:46:49,000
Speaker 4: you just have neutral iron. How does that generate a

1029
00:46:49,000 --> 00:46:49,760
Speaker 4: magnetic field?

1030
00:46:49,920 --> 00:46:52,040
Speaker 6: Yeah, it's actually an induction process.

1031
00:46:52,080 --> 00:46:54,040
Speaker 7: So what it is is you've got a good electrical

1032
00:46:54,080 --> 00:46:57,799
Speaker 7: conductor and imagine you have a magnetic field and it's

1033
00:46:57,840 --> 00:47:01,600
Speaker 7: frozen into a good electrical conductor. So magnetic fields tend

1034
00:47:01,640 --> 00:47:03,200
Speaker 7: to stick inside good conductors.

1035
00:47:03,200 --> 00:47:04,120
Speaker 6: They don't like to change.

1036
00:47:04,200 --> 00:47:07,120
Speaker 7: But imagine then that you start moving that conductor around

1037
00:47:07,200 --> 00:47:09,160
Speaker 7: relative to itself, so you shear it, you pull it

1038
00:47:09,200 --> 00:47:11,359
Speaker 7: apart a little bit. That magnetic field has to go

1039
00:47:11,440 --> 00:47:14,480
Speaker 7: with it, so you stretch and twist the magnetic fields

1040
00:47:14,520 --> 00:47:17,520
Speaker 7: through the motion itself to create new magnetic fields.

1041
00:47:17,640 --> 00:47:22,200
Speaker 4: Wow. Fascinating. And the Earth's magnetic field, though it's pretty reliable,

1042
00:47:22,320 --> 00:47:24,680
Speaker 4: is not actually constant. Isn't it gradually changing?

1043
00:47:24,880 --> 00:47:25,880
Speaker 6: Yes? Absolutely so.

1044
00:47:25,920 --> 00:47:29,399
Speaker 7: We have records from the rocks in our crust. They

1045
00:47:29,480 --> 00:47:32,600
Speaker 7: can be magnetized at the time that they form, and

1046
00:47:33,120 --> 00:47:36,120
Speaker 7: those records tell us that Earth's magnetic field has changed

1047
00:47:36,160 --> 00:47:38,319
Speaker 7: over time. We at least have data that shows it's

1048
00:47:38,360 --> 00:47:40,960
Speaker 7: been around for about three billion years, if not longer.

1049
00:47:41,840 --> 00:47:43,640
Speaker 7: But it hasn't always been the same, So there are

1050
00:47:43,640 --> 00:47:45,600
Speaker 7: times in the past where the field has gotten weaker.

1051
00:47:45,680 --> 00:47:48,000
Speaker 7: There are times in the past where the field has

1052
00:47:48,080 --> 00:47:50,879
Speaker 7: flipped polarity, so the north magnetic pole became the south

1053
00:47:50,960 --> 00:47:54,600
Speaker 7: magnetic pole and vice versa. And even today, on like

1054
00:47:55,200 --> 00:47:58,360
Speaker 7: weekly time scales, we can measure the small changes in

1055
00:47:58,400 --> 00:48:00,760
Speaker 7: the earth magnetic field that are happening from a variety

1056
00:48:00,760 --> 00:48:03,040
Speaker 7: of things. Some things are external, but sometimes we can

1057
00:48:03,080 --> 00:48:05,680
Speaker 7: also see on a yearly scale we can see the

1058
00:48:05,760 --> 00:48:08,400
Speaker 7: changes due to different flows happening in the core of

1059
00:48:08,400 --> 00:48:08,840
Speaker 7: the Earth.

1060
00:48:09,000 --> 00:48:11,200
Speaker 4: Can we use these changes in the magnetic field to

1061
00:48:11,200 --> 00:48:13,520
Speaker 4: sort of image those flows the same way we can

1062
00:48:13,760 --> 00:48:16,160
Speaker 4: see changes in the gravitational field to give us a

1063
00:48:16,160 --> 00:48:17,399
Speaker 4: picture of what's inside the Earth.

1064
00:48:17,480 --> 00:48:20,480
Speaker 7: Yeah, it gets a little more challenging the deeper you go.

1065
00:48:20,680 --> 00:48:23,120
Speaker 7: And with magnetic fields, what we can see, for example,

1066
00:48:23,280 --> 00:48:25,480
Speaker 7: is because we know it's a good electrical conductor, if

1067
00:48:25,520 --> 00:48:28,280
Speaker 7: we see a magnetic field pattern drifting in one direction.

1068
00:48:28,600 --> 00:48:30,840
Speaker 7: So for example, there's this kind of famous thing we

1069
00:48:30,880 --> 00:48:34,160
Speaker 7: talk about in geomagnetism called the westward drift. So if

1070
00:48:34,200 --> 00:48:36,239
Speaker 7: you follow certain features of the magnetic field, you see

1071
00:48:36,239 --> 00:48:38,920
Speaker 7: they all kind of drift westward, and we interpret that

1072
00:48:38,960 --> 00:48:41,520
Speaker 7: to being there's flow generally in the westward direction.

1073
00:48:41,600 --> 00:48:44,360
Speaker 6: There's like a jet stream in the core of.

1074
00:48:44,360 --> 00:48:47,480
Speaker 7: The Earth that's flowing westward, that's taking the magnetic field

1075
00:48:47,480 --> 00:48:47,839
Speaker 7: with us.

1076
00:48:47,880 --> 00:48:50,720
Speaker 4: Wow, and so how well do we understand this process?

1077
00:48:50,760 --> 00:48:53,760
Speaker 4: Are there still open questions about like why it's flipping

1078
00:48:53,800 --> 00:48:55,840
Speaker 4: and why it's changing or is it something that we

1079
00:48:55,920 --> 00:48:56,839
Speaker 4: understand pretty well?

1080
00:48:57,000 --> 00:49:00,520
Speaker 7: So many open questions. So the amazing thing about the process,

1081
00:49:00,560 --> 00:49:03,320
Speaker 7: so fluid dynamics. If you've had any experience with climate

1082
00:49:03,360 --> 00:49:06,680
Speaker 7: modeling or trying to study flows that happen in pipes

1083
00:49:06,719 --> 00:49:10,759
Speaker 7: and so forth, fluids are really complicated. They can they

1084
00:49:10,760 --> 00:49:14,600
Speaker 7: can display turbulence, for example, or laminar flows depending on

1085
00:49:14,640 --> 00:49:18,080
Speaker 7: what types of you know, what the situation is like.

1086
00:49:18,800 --> 00:49:19,839
Speaker 6: Now, if you add to.

1087
00:49:19,800 --> 00:49:23,000
Speaker 7: That, add to fluid dynamics magnetic fields and all the

1088
00:49:23,080 --> 00:49:25,239
Speaker 7: things that happen with magnetic fields, you almost get an

1089
00:49:25,280 --> 00:49:28,600
Speaker 7: added complication. And so when we try to think about, well,

1090
00:49:28,600 --> 00:49:30,920
Speaker 7: how do we study the dynamo process, right, we can't

1091
00:49:30,920 --> 00:49:34,000
Speaker 7: really wait thousands of years to watch the real system

1092
00:49:34,040 --> 00:49:36,279
Speaker 7: over time. We want to study it faster. So you

1093
00:49:36,320 --> 00:49:39,239
Speaker 7: can either do experiments or you can try to write

1094
00:49:39,239 --> 00:49:42,279
Speaker 7: a computer model that can mimic what's going on in

1095
00:49:42,320 --> 00:49:45,759
Speaker 7: a core when it's generating a magnetic field. Experiments are

1096
00:49:45,760 --> 00:49:49,800
Speaker 7: really hard. Turns out that dynamos they like three things.

1097
00:49:50,000 --> 00:49:53,840
Speaker 7: They like really good electrical conductors, they like really fast motions,

1098
00:49:53,880 --> 00:49:56,279
Speaker 7: and they like really large length scales. And then you

1099
00:49:56,320 --> 00:49:59,600
Speaker 7: start saying, Okay, I'm going to build my giant sphere

1100
00:50:00,320 --> 00:50:02,799
Speaker 7: of a really good electrical conductor and then spin it

1101
00:50:02,840 --> 00:50:05,040
Speaker 7: really fast, and you just you end up with a

1102
00:50:05,120 --> 00:50:08,680
Speaker 7: huge challenging problem. The biggest dynamo experiment out there is

1103
00:50:08,719 --> 00:50:12,399
Speaker 7: the three meter dynamosphere in Maryland, and it has yet

1104
00:50:12,440 --> 00:50:16,400
Speaker 7: to generate an active dynamo, so that's a challenging problem.

1105
00:50:16,760 --> 00:50:19,719
Speaker 7: We use computer simulations to study dynamos inside planets. The

1106
00:50:19,800 --> 00:50:23,880
Speaker 7: problem there is that planets, the motions, the scales, and

1107
00:50:23,920 --> 00:50:26,640
Speaker 7: the motions are so tiny and so fast that there

1108
00:50:26,680 --> 00:50:29,080
Speaker 7: isn't enough computer power on the planet to run a

1109
00:50:29,120 --> 00:50:31,440
Speaker 7: simulation accurately. So we have to make a lot of

1110
00:50:31,480 --> 00:50:35,719
Speaker 7: assumptions and simplifying type conditions, so we aren't able to

1111
00:50:35,719 --> 00:50:37,000
Speaker 7: fully study the system.

1112
00:50:36,760 --> 00:50:38,239
Speaker 6: The way we want to. We have to be very

1113
00:50:38,800 --> 00:50:40,400
Speaker 6: nuanced in how we study it. Well.

1114
00:50:40,440 --> 00:50:43,600
Speaker 4: Do we understand why the Earth's flipping of the magnetic

1115
00:50:43,680 --> 00:50:46,319
Speaker 4: field seems so irregular compared to, for example, the Sun,

1116
00:50:46,360 --> 00:50:49,240
Speaker 4: which has this rock solid solar cycle of eleven years.

1117
00:50:49,400 --> 00:50:52,040
Speaker 7: Yeah, we don't fully understand why at all. We can't

1118
00:50:52,080 --> 00:50:54,279
Speaker 7: even kind of predict what we would expect for other

1119
00:50:54,320 --> 00:50:56,160
Speaker 7: planets as well. We have what I would call a

1120
00:50:56,200 --> 00:50:59,239
Speaker 7: hand way the understanding, and that we would describe the

1121
00:50:59,239 --> 00:51:02,960
Speaker 7: core fluid as being a very nonlinear system that can

1122
00:51:03,040 --> 00:51:07,600
Speaker 7: have different attractors or different stable systems. And sometimes it's

1123
00:51:07,640 --> 00:51:10,120
Speaker 7: in one stable position, sometimes it's another. And so if

1124
00:51:10,120 --> 00:51:12,239
Speaker 7: you have something near a stable position, imagine you have

1125
00:51:12,280 --> 00:51:15,960
Speaker 7: a ball sitting and you have like a nice valley

1126
00:51:15,960 --> 00:51:17,719
Speaker 7: and two hills on the side, and you stick the

1127
00:51:17,719 --> 00:51:20,080
Speaker 7: ball on one of the tops of the hills, right,

1128
00:51:20,120 --> 00:51:22,239
Speaker 7: it'll pretty much stay there. But maybe if you shake

1129
00:51:22,280 --> 00:51:23,719
Speaker 7: it a little bit too much, give it a bit

1130
00:51:23,760 --> 00:51:26,480
Speaker 7: too many perturbations, it'll sink down and go to the

1131
00:51:26,520 --> 00:51:30,080
Speaker 7: other stable position. So we think that some perturbations in

1132
00:51:30,120 --> 00:51:32,920
Speaker 7: the fluid can sometimes cause the field of flip, but

1133
00:51:33,040 --> 00:51:34,840
Speaker 7: we don't have a good way to, for example, predict

1134
00:51:34,920 --> 00:51:36,920
Speaker 7: when the next flip is going to happen, what's the

1135
00:51:37,200 --> 00:51:39,760
Speaker 7: key factor that causes such a flip for example?

1136
00:51:39,760 --> 00:51:41,280
Speaker 6: And these are all areas of current research.

1137
00:51:41,400 --> 00:51:45,920
Speaker 4: Wow. And then as we discover planets in other solar systems.

1138
00:51:46,200 --> 00:51:49,640
Speaker 4: How do we begin to do geology of those planets?

1139
00:51:49,640 --> 00:51:52,040
Speaker 4: And first, I guess it's a trivial question, is would

1140
00:51:52,040 --> 00:51:54,200
Speaker 4: you call it geology? Geology is to study the Earth,

1141
00:51:54,239 --> 00:51:56,920
Speaker 4: So is this like exo planetology? What do you call it?

1142
00:51:57,120 --> 00:51:58,360
Speaker 6: This is a great question.

1143
00:51:58,480 --> 00:52:01,319
Speaker 7: I think the norm has been to refer to geology

1144
00:52:01,400 --> 00:52:03,799
Speaker 7: as looking at rocks, and it doesn't matter where those

1145
00:52:03,880 --> 00:52:04,279
Speaker 7: rocks are.

1146
00:52:04,320 --> 00:52:04,960
Speaker 6: So rocks.

1147
00:52:05,120 --> 00:52:07,399
Speaker 7: There are Mars geologists, so I'll just get that out

1148
00:52:07,400 --> 00:52:11,239
Speaker 7: there instead of marsologists or whatever you would call them instead. Yeah,

1149
00:52:11,280 --> 00:52:15,000
Speaker 7: with exoplanets, the challenge there is the type of information

1150
00:52:15,080 --> 00:52:17,360
Speaker 7: you can get can be quite limited compared to what

1151
00:52:17,400 --> 00:52:19,640
Speaker 7: we can get when we're in our own Solar system

1152
00:52:19,719 --> 00:52:22,240
Speaker 7: or here on the Earth. But even with the standard

1153
00:52:22,239 --> 00:52:26,360
Speaker 7: techniques that can discover exoplanets, right, if you think about

1154
00:52:26,560 --> 00:52:29,880
Speaker 7: the methods involving radial velocity detection, so where you measure

1155
00:52:29,960 --> 00:52:33,520
Speaker 7: fluctuations in the stars light curve caused by the motion

1156
00:52:33,680 --> 00:52:35,880
Speaker 7: of a planet around it, you get information about the

1157
00:52:35,880 --> 00:52:38,160
Speaker 7: period of the orbit, and that can also give you

1158
00:52:38,400 --> 00:52:41,319
Speaker 7: measurements about the mass of the planet. Then if you

1159
00:52:41,440 --> 00:52:44,040
Speaker 7: use transit where a planet passes in front of or

1160
00:52:44,040 --> 00:52:46,640
Speaker 7: behind a star, you can get information about the size

1161
00:52:46,680 --> 00:52:47,280
Speaker 7: of the planet.

1162
00:52:47,440 --> 00:52:48,239
Speaker 6: So as soon as you have.

1163
00:52:48,200 --> 00:52:49,920
Speaker 7: The size and the mass, you already have kind of

1164
00:52:49,960 --> 00:52:52,920
Speaker 7: an average density, a bulk density of the planet. So

1165
00:52:52,960 --> 00:52:56,200
Speaker 7: we have sense of whether when we discover these exoplanets,

1166
00:52:56,480 --> 00:52:59,880
Speaker 7: is it a gas giant, is it an Earth like planet?

1167
00:53:00,080 --> 00:53:02,279
Speaker 7: Is it an ice world like Uranus and Neptune. So

1168
00:53:02,320 --> 00:53:06,080
Speaker 7: we can do some very broad geology, let's say, from

1169
00:53:06,120 --> 00:53:09,200
Speaker 7: that type of information. But what I'm most excited about

1170
00:53:09,360 --> 00:53:11,759
Speaker 7: is the possibilities that are going to come forward with

1171
00:53:11,880 --> 00:53:16,359
Speaker 7: JWST because this new telescope is going to be able

1172
00:53:16,360 --> 00:53:21,200
Speaker 7: to measure the atmospheres of exoplanets and tell us what

1173
00:53:21,239 --> 00:53:23,920
Speaker 7: they're made of. That's going to be crucial information to

1174
00:53:23,960 --> 00:53:26,760
Speaker 7: figure out what's actually going on deeper inside the planet.

1175
00:53:26,880 --> 00:53:29,560
Speaker 7: Right our atmosphere on Earth is the way it is

1176
00:53:29,640 --> 00:53:32,279
Speaker 7: because of interactions with the interior of the Earth, and

1177
00:53:32,320 --> 00:53:34,120
Speaker 7: so we're going to be able to use information about

1178
00:53:34,120 --> 00:53:36,600
Speaker 7: the atmospheres of these exoplanets to also tell us something

1179
00:53:36,600 --> 00:53:37,520
Speaker 7: about the interior.

1180
00:53:37,560 --> 00:53:39,520
Speaker 4: What do you mean by that? I know our atmosphere

1181
00:53:39,640 --> 00:53:42,160
Speaker 4: is different because we have a magnetic field and because

1182
00:53:42,160 --> 00:53:45,520
Speaker 4: of the surface gravity. What else does our atmosphere tell

1183
00:53:45,560 --> 00:53:46,960
Speaker 4: us about what's inside the Earth.

1184
00:53:47,120 --> 00:53:50,080
Speaker 7: Right, So if there was an alien flying by our

1185
00:53:50,080 --> 00:53:52,520
Speaker 7: solar system, and all it could measure is kind of

1186
00:53:52,560 --> 00:53:54,840
Speaker 7: the spectrum of our atmosphere, it would be able to

1187
00:53:54,880 --> 00:53:56,680
Speaker 7: tell that there was life here most likely.

1188
00:53:56,760 --> 00:53:56,920
Speaker 8: Right.

1189
00:53:56,920 --> 00:53:59,560
Speaker 7: We've done things to our environment to make it very

1190
00:53:59,640 --> 00:54:03,400
Speaker 7: obvious that there is industrial action happening on the surface.

1191
00:54:03,520 --> 00:54:03,759
Speaker 6: Right.

1192
00:54:03,840 --> 00:54:07,040
Speaker 7: But also, for example, a lot of the processes that

1193
00:54:07,200 --> 00:54:10,319
Speaker 7: regulate some of the key species in our atmospheres, like

1194
00:54:10,320 --> 00:54:14,600
Speaker 7: carbon dioxide. On Earth, there's the carbon cycle. The carbon

1195
00:54:14,640 --> 00:54:17,840
Speaker 7: cycle not only involves the atmosphere, it involves the ocean,

1196
00:54:18,160 --> 00:54:21,920
Speaker 7: the surface, and the deep interior. So carbon gets recycled

1197
00:54:22,320 --> 00:54:25,520
Speaker 7: inside the Earth, and so we can actually learn about

1198
00:54:25,640 --> 00:54:28,880
Speaker 7: how exchanges of materials happen with the interior and the

1199
00:54:28,920 --> 00:54:31,760
Speaker 7: atmosphere by looking at how much carbon there is around,

1200
00:54:31,760 --> 00:54:33,840
Speaker 7: for example, right. And so the same is true for

1201
00:54:33,960 --> 00:54:36,959
Speaker 7: other element cycles, and so the same could be true

1202
00:54:36,960 --> 00:54:37,759
Speaker 7: for exoplanets.

1203
00:54:37,840 --> 00:54:41,000
Speaker 4: We had Professor Shields on the podcast recently, and she

1204
00:54:41,120 --> 00:54:45,640
Speaker 4: does exoplanet climate simulations. We're basically building models of these

1205
00:54:45,680 --> 00:54:48,440
Speaker 4: planets and then trying to make them consistent with what

1206
00:54:48,480 --> 00:54:51,279
Speaker 4: we might understand from JWST. It sounds like you're talking

1207
00:54:51,320 --> 00:54:53,759
Speaker 4: about doing something similar, but you're building models of the

1208
00:54:53,760 --> 00:54:56,920
Speaker 4: internals of these planets to explain then the climate in

1209
00:54:56,960 --> 00:54:59,520
Speaker 4: the atmosphere, which then tells us about the light we're

1210
00:54:59,560 --> 00:55:01,560
Speaker 4: seeing from these planets. So it seems like quite a

1211
00:55:01,600 --> 00:55:04,560
Speaker 4: few steps there from the photons we're getting in Jast

1212
00:55:04,960 --> 00:55:07,960
Speaker 4: to our model of what's happening inside those planets. Incredible

1213
00:55:07,960 --> 00:55:08,680
Speaker 4: that we could learn.

1214
00:55:08,560 --> 00:55:10,120
Speaker 6: Anything, Yes, absolutely agreed.

1215
00:55:10,280 --> 00:55:12,720
Speaker 4: And what about future missions? I know there are space

1216
00:55:12,760 --> 00:55:15,320
Speaker 4: telescopes that are going to be looking specifically for planets.

1217
00:55:15,360 --> 00:55:17,480
Speaker 4: Are those going to have the capacity to tell us

1218
00:55:17,520 --> 00:55:19,799
Speaker 4: more about these planets or do we need to wait

1219
00:55:19,880 --> 00:55:24,240
Speaker 4: until we can send the landers to listen for exoplanet quakes.

1220
00:55:24,320 --> 00:55:28,520
Speaker 7: What I'm most excited about for future exoplanet data has

1221
00:55:28,560 --> 00:55:30,719
Speaker 7: to do with magnetic fields again, right, So if we

1222
00:55:30,800 --> 00:55:34,080
Speaker 7: think Earth having a magnetic field is so important for

1223
00:55:34,200 --> 00:55:36,719
Speaker 7: shielding life on the surface, then it might be nice

1224
00:55:36,760 --> 00:55:39,160
Speaker 7: if we knew that exoplanets had magnetic fields.

1225
00:55:39,160 --> 00:55:40,400
Speaker 6: It maybe it's something we should.

1226
00:55:40,120 --> 00:55:42,800
Speaker 7: Add to the conditions for a habitable planet out there.

1227
00:55:43,120 --> 00:55:45,440
Speaker 7: And there have been some signs, some evidence that we

1228
00:55:45,520 --> 00:55:48,200
Speaker 7: might actually be able to measure magnetic fields of exoplanets

1229
00:55:48,400 --> 00:55:52,080
Speaker 7: so there's hope that with even more measurements and so forth,

1230
00:55:52,400 --> 00:55:54,840
Speaker 7: we might actually be able to tell in the future

1231
00:55:54,920 --> 00:55:56,920
Speaker 7: if an exoplanet has a magnetic field.

1232
00:55:56,680 --> 00:55:58,719
Speaker 4: Today, how would that be possible? Are you looking for

1233
00:55:58,800 --> 00:56:01,759
Speaker 4: like the Northern La It's equivalent on the planet seeing

1234
00:56:01,760 --> 00:56:03,799
Speaker 4: the effect of the magnetic field on the atmosphere.

1235
00:56:03,840 --> 00:56:05,680
Speaker 7: So that's one way kind of so it's not the

1236
00:56:05,719 --> 00:56:08,680
Speaker 7: Northern Light itself. But actually the way we found out

1237
00:56:08,760 --> 00:56:10,600
Speaker 7: Jupiter had a magnetic field. We knew that Jupiter had

1238
00:56:10,600 --> 00:56:12,719
Speaker 7: a magnet field in the nineteen sixties even though we'd

1239
00:56:12,719 --> 00:56:17,640
Speaker 7: never been there, because electrons that spiral along the magnetic

1240
00:56:17,680 --> 00:56:20,360
Speaker 7: field lines of Jupiter get really close to the poles

1241
00:56:20,520 --> 00:56:22,600
Speaker 7: into the atmosphere there, right, and that causes aurora on

1242
00:56:22,680 --> 00:56:25,520
Speaker 7: Jupiter as well. But it also causes a type of

1243
00:56:25,840 --> 00:56:28,879
Speaker 7: radio emissions to come off of Jupiter, and those radio

1244
00:56:28,880 --> 00:56:31,200
Speaker 7: emissions get beamed out into space and we could actually

1245
00:56:31,239 --> 00:56:33,160
Speaker 7: measure them here on the surface of the Earth. So

1246
00:56:33,200 --> 00:56:35,800
Speaker 7: we knew about Jupiter's magnetic field in the nineteen sixties

1247
00:56:35,800 --> 00:56:38,640
Speaker 7: before we'd ever gone there, because we received these radio emissions.

1248
00:56:38,960 --> 00:56:41,880
Speaker 7: Same is true for any other planet. Now, it turns

1249
00:56:41,880 --> 00:56:44,840
Speaker 7: out that the intensity of those radio emissions is really important,

1250
00:56:44,880 --> 00:56:46,880
Speaker 7: so you need really strong magnetic fields in order to

1251
00:56:46,880 --> 00:56:48,600
Speaker 7: be able to measure them. On the surface of the Earth,

1252
00:56:48,800 --> 00:56:51,000
Speaker 7: we have this horrible atmosphere on Earth and it blocks

1253
00:56:51,040 --> 00:56:53,640
Speaker 7: a lot of radio emissions, which is very frustrating, although

1254
00:56:53,760 --> 00:56:55,640
Speaker 7: kind of good for breathing. So I guess, you know,

1255
00:56:59,000 --> 00:57:00,759
Speaker 7: let's say we put a radio telescope on the far

1256
00:57:00,840 --> 00:57:03,640
Speaker 7: side of the Moon. That would be great for helping

1257
00:57:03,640 --> 00:57:07,400
Speaker 7: to detect radio emissions from exoplanets. So there's that method,

1258
00:57:07,480 --> 00:57:10,040
Speaker 7: but they're also what I would call sneakier methods.

1259
00:57:10,120 --> 00:57:10,319
Speaker 6: Right.

1260
00:57:10,600 --> 00:57:14,360
Speaker 7: For example, if you look at the transit spectrum, so

1261
00:57:14,360 --> 00:57:16,120
Speaker 7: if you look at a planet that's going in front

1262
00:57:16,120 --> 00:57:19,920
Speaker 7: of a sun or a star and you see kind

1263
00:57:19,960 --> 00:57:22,480
Speaker 7: of how wide the planet is. People can already kind

1264
00:57:22,480 --> 00:57:24,920
Speaker 7: of tell if a planet has an atmosphere by the

1265
00:57:24,920 --> 00:57:28,080
Speaker 7: fact that it could have different thicknesses or different radius

1266
00:57:28,120 --> 00:57:31,400
Speaker 7: in different wavelengths, and that you know, sometimes the atmosphere

1267
00:57:31,440 --> 00:57:34,720
Speaker 7: will let light through, whereas the planet itself won't, right,

1268
00:57:34,760 --> 00:57:36,760
Speaker 7: And so that's how we can tell whether something has

1269
00:57:36,800 --> 00:57:39,720
Speaker 7: an atmosphere, is what particular wavelengths of light get through

1270
00:57:39,720 --> 00:57:42,040
Speaker 7: at different distances. The same can be true about a

1271
00:57:42,040 --> 00:57:44,959
Speaker 7: magnetic field. Sometimes a magnetic field can cause certain light

1272
00:57:45,080 --> 00:57:47,760
Speaker 7: spectra light frequencies to not get through, so we might

1273
00:57:47,800 --> 00:57:51,960
Speaker 7: be actually able to measure a magnetosphere surrounding a planet

1274
00:57:52,600 --> 00:57:55,760
Speaker 7: by looking at transit spectra. You can also maybe see

1275
00:57:55,800 --> 00:57:58,440
Speaker 7: if a planet has like a tail, right, and so

1276
00:57:58,760 --> 00:58:01,240
Speaker 7: sometimes if atmosphere is be blown off a planet, you

1277
00:58:01,320 --> 00:58:03,320
Speaker 7: might be able to see that in a transit spectrum

1278
00:58:03,400 --> 00:58:06,560
Speaker 7: or through other types of light detection. So there might

1279
00:58:06,560 --> 00:58:08,800
Speaker 7: be some sneaky ways to look for magnet fields of

1280
00:58:08,800 --> 00:58:09,720
Speaker 7: extle plants as well.

1281
00:58:10,200 --> 00:58:12,960
Speaker 4: Wonderful well, I expect that the next generation of scientists

1282
00:58:12,960 --> 00:58:15,080
Speaker 4: will be even more creative about coming up with ways

1283
00:58:15,120 --> 00:58:18,920
Speaker 4: to extract amazing information from these tiny little blips in

1284
00:58:18,960 --> 00:58:19,680
Speaker 4: our telescopes.

1285
00:58:19,840 --> 00:58:20,520
Speaker 6: Yes, hopefully so.

1286
00:58:20,760 --> 00:58:22,600
Speaker 4: Wonderful well, thank you very much for coming on the

1287
00:58:22,640 --> 00:58:24,800
Speaker 4: podcast and telling us so much about the mysteries that

1288
00:58:24,800 --> 00:58:26,919
Speaker 4: are under our feet and the mysteries that are out

1289
00:58:26,920 --> 00:58:27,920
Speaker 4: there in the universe.

1290
00:58:28,120 --> 00:58:28,640
Speaker 6: Thanks so much.

1291
00:58:28,680 --> 00:58:30,760
Speaker 4: This was fun, all right. That was my chat with

1292
00:58:30,800 --> 00:58:33,560
Speaker 4: Professor Sabina Stanley again. She's the author of the book

1293
00:58:33,680 --> 00:58:37,000
Speaker 4: What's Hidden Inside Plants, which you can get now at

1294
00:58:37,040 --> 00:58:40,600
Speaker 4: all reputable booksellers. Thanks very much for listening. Tune in

1295
00:58:40,680 --> 00:58:50,960
Speaker 4: next time. Thanks for listening, and remember that Daniel and

1296
00:58:51,040 --> 00:58:54,360
Speaker 4: Jorge Explain the Universe is a production of iHeart Radio.

1297
00:58:54,600 --> 00:58:59,120
Speaker 4: For more podcasts from iHeartRadio, visit the iHeartRadio app Apple

1298
00:58:59,160 --> 00:59:02,280
Speaker 4: Podcasts wherever you listen to your favorite shows.

1299
00:59:13,360 --> 00:59:15,760
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